(ENCORE) Why is Kitchen Ventilation So Important? With Dr. Iain Walker from LBNL

We first released this episode in April 2019. Since then, our topic of discussion with Iain has only become more relevant. We recently caught up with Iain and have some updates to share, which are reflected in the resources below and at the end of the episode. Enjoy!

When you fire on a stove-top burner, whether it is electric, gas, or convection, many byproducts are released. This increase in moisture, gas, and other particulates is not only detrimental to the health of a building, but dangerous for human health as well.

To advance our knowledge on this topic, we invited building scientist and ventilation expert, Dr. Iain Walker, from Lawrence Berkeley National Laboratory (LBNL). Dr. Walker discusses strategies for controlling byproducts associated with cooking by focusing on kitchen ventilation.

Episode Guests: Iain Walker, PhD.

Iain Walker HeadshotIain Walker is a scientist at Lawrence Berkeley National Laboratory (LBNL). He has more than 20 years of experience as a building scientist and consultant, conducting research on energy use, ventilation, moisture, performance simulation, and commissioning/diagnostic issues in residential buildings. His current work focuses on retrofits, zero/low-energy homes and heating, ventilation, and air-conditioning (HVAC) systems in residential buildings through field and laboratory evaluations, modeling and simulation activities, and standards setting. Dr. Walker is the task group leader for the American Society of Testing and Materials (ASTM) standards committees on building and duct system air leakage and sealant longevity. For the American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) he serves on National Standards committees for indoor air quality, weather, moisture design, and equipment air leakage. He also serves on Building Performance Institute (BPI) and Residential Energy Services Network (RESNET) Technical Committees, the Affordable Comfort (ACI) conference planning committee and provides leadership and technical input to many local, state, national and international bodies.

Episode Information & Resources

New Resources as of 8/3/21:

Simulation of short-term exposure to NO2 and PM2.5 to inform capture efficiency standards

Effects of Residential Gas Appliances on Indoor and Outdoor Air Quality and Public Health in California

Investigating Emissions from the Cooking of Meals

Ultrafine Particles from Electric Appliances and Cooking Pans

Reducing Exposure to Cooking Pollutants – Policies and Practices


Indoor Air Quality: Residential Cooking Exposures 

Measurement of Ultrafine Particles and Other Air Pollutants Emitted by Cooking Activities

Particle Concentrations in Inner-city Homes of Children with Asthma…

Impact of Natural Gas Appliances on Pollutant Levels in California Homes

Indoor Air Quality in 24 California Residences Designed as High Performance Green Homes


HVI Guide

HVI Products Directory


ANSI/ASHRAE Standards for Ventilation and Indoor Air Quality

ANSI/BPI: Home Energy Auditing Standard

ANSI/BPI: Standard Practice for Basic Analysis of Buildings

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Buildings and Beyond is a production of Steven Winter Associates. We provide energy, green building, and accessibility consulting services to improve the built environment. For more information, visit


Robb Aldrich | Kelly Westby

Production Team

Heather Breslin | Alex Mirabile | Dylan Martello | Jayd Alvarez

Episode Transcript

Robb (00:00):

It’s summer 2021. And we have a couple of new guests lined up for our August episode, but scheduling and vacations just didn’t work out. So we are posting an episode from a couple of years ago where Kelly talked with Iain Walker about kitchen ventilation. We all really liked this episode and it’s really relevant to anyone who cooks or lives with someone who cooks. We reached out to Iain about any new developments on this front and I’ll recap what he had to say at the end and the outro. And we also have some new links in the show notes for more information. So here’s Kelly’s conversation with Iain Walker.

Ian:                                    00:42                   They should care because the idea is that when you cook, it’s basically one of the activities that you do that emits the most contaminants into, into your home and by contaminants- there are some pretty straightforward ones. Like there’s lots of water vapor when you’re cooking and if you don’t wanna have condensation on your windows in the winter for example, or you don’t want to make your house get too humid, so you might get some mold growth. Do you want to control the humidity levels in it? It’s a good idea to vent the moisture from cooking to outside. Then you have to think about odors. And of course, you know, some odors are good when, when you’re cooking, right? The, the odor is what makes you know, home cooking worthwhile sometimes and what’s make makes food tastes nice and everything. But if you’ve been frying fish one day, maybe you don’t want the smell of fried fish in your house for the next few days. And the last thing is more from a health perspective, which is that aside from the moisture and odor issues there are contaminants admitted when you cook that can actually impact your health. One of the primary ones is small particles and they come from either the burning of natural gas if you’re using a gas cooktop, or the cooking process itself. And then there are things like oxides of nitrogen that also are emitted from from gas burners. And those contaminants are ones that if they get to a high enough concentration can have some health impacts. So there’s a good health reason for venting most of those things to outside. And so it’s a combination of you want to control moisture in your home, you want to control odors in your home, and there’s a health impact also. And I’m not saying that you shouldnt cook. I personally love cooking and everybody should cook. I think a home cooked meal is probably the healthiest way to feed yourself, but we should do it with an awareness that it’s a good idea to control what we do when we’re cooking. And effectively the best way to do it is to vent some of these things to outside. So that’s the rationale for why you would vent a kitchen ever. And if you’ve ever been in a commercial kitchen, you’ll see that they have enormous range heads with huge amounts of flow and they’re physically large and they have gigantic makeup air systems and if you’re cooking all the time, they make a huge effort to vent the cooking to outside. Of course we cook less in our homes, but the principles behind it are for the same reason. It’s about controlling the moisture odor, and some of these contaminants that can have health impacts.

Kelly:                                  03:22                   Now, Ian Walker, who you just heard is a scientist at Lawrence Berkeley National Laboratory, LBNL. He works as a building scientist and consultant conducting research on energy use, ventilation, moisture performance simulation and commissioning diagnostic issues in residential buildings. I encourage you to go to the show notes and look at the link to LBNL’s website. It turns out Ian has been doing ventilation research papers dating back to 1990. Whether you cook once in awhile or you cook all the time, whether you live in an apartment or a house, whether you have no renovation budget or unlimited- stay tuned, there will be something in this episode for you. I’ll let Ian give you a little background and lay the groundwork for you. So we’re going to jump right in.

Ian:                                    04:07                   Kitchen ventilation is not a new thing, right? It’s been around for a long, long time. But it’s only recently that we’ve done anything about it and in a way where we could actually put some numbers to it. And by that I mean kitchen rangers had been used and just, you know, simple vents and kitchens have been around for thousands of years. But actual kitchen rangers with a fan in them have been around for a while. But how good are they and how much of the contaminants they capture has been something that hasn’t really been studied until recently. And what we were really looking for was a way to figure out how well these devices work with a longer term goal of maybe we could make them work better even though they moved less air for example, because there surely is an energy penalty just in the fan power and also heating and cooling all that air that you’re exhausting. Right. So that’s why we wanted to like actually put some numbers on how well a range hoods work and try and figure out is there something about the geometry or the amount of airflow that makes some work better and some not and so on.

Kelly:                                  05:13                   Great. Yeah. And mostly, the research is looking at single family or low rise multifamily?

Ian:                                    05:22                   Well I wouldn’t say necessarily- no. I think, I everybody’s kitchen should get some good ventilation so I wouldn’t restrict it. But you raise a good point, which is it’s easier in some buildings than others, right? In a house, having an exhaust fan in your kitchen is not too difficult to conceive of. Right? Maybe you have to cut a hole in the wall or maybe in the ceiling if you’re gonna go out through the ceiling, put some ducting in. Seems pretty straight forward. But in a high rise building, it can be a little trickier. Often highrise architecture is much more sensitive to having lots of holes in the wall. And then if you’ve got many, many stories all stacked up on top of each other, you’ve got to find room for all that ducting in the end. And it does get a little more complex from an engineering perspective, but not impossible.

Kelly:                                  06:12                   So now say I’m a homeowner and maybe I don’t have any renovation budget, but what should I think about when I go to Cook my dinner tonight?

Ian:                                    06:22                   Well there’s some simple things you can do if you’re not going to remodel your kitchen or replace the range hood. The first thing, is you should know if your range ofvents to outside, that’s the first question there. There are many hoods over cooktops that just blow the air back into the kitchen and they’re not particularly effective at doing anything for controlling the things I just talked about. As you imagine, they just blow the moisture straight back in. They don’t do much for removing things like particles, oxides of nitrogen and they don’t control odor as much. They often will have a grease filter in, right, that you’ve probably seen, these sort of metal things. If you look underneath your hood, you’ll see this sort of metal grate and so it might stop some of the grease getting circulated your kitchen, But for the other stuff, it doesn’t do much. So first of all, you need to have something that vents to outside. If it’s just blowing back and greasing your forehead, then I’m ambivalent about whether you use it or not. It’s totally up to you. But I don’t think it’s doing very much. So As long as vents to outside, the first thing is to turn it on. And even the very worst hood is going to be better than not using it. So even if you think you have a bad one, try using it. The next thing is, if we’re talking now about a cooktop that’s up against the wall with a hood above it also mounted on the wall, they always do better at capturing from the burners at the back than the front. So if you can cook on the back burners it’s going to be way better. Of course, that’s also the most awkward way to cook. And so most people cook on the front burners for convenience. And so it’s always gonna be a personal tradeoff, but certainly using the back burners is going to be better for your range hood for getting it to to capture what’s on the cooktop. So even if you do nothing in your kitchen, you can at least turn it on and cook on the back burners. And, and that’s, that’s a big step forward.

Kelly:                                  08:18                   Awesome. That’s great. That’s great advice. And then I guess taking the next step, if I’ve maybe convinced my partner that we should decide to renovate our kitchen and we maybe have some renovation budget now, what should we look at or what should we talk to our builder about?

Ian:                                    08:36                   So here you’re talking about how do I pick my new range hood effectively? And there’s a couple of things you can do, that when you’re browsing through catalogs or you’re at the hardware store looking at these things. One is to simply look at the physical geometry of the hood. And the key thing is, does it come out far enough from the wall to cover all the burners? And basically the further out from the wall it comes, the more coverage it has generally speaking, the better it will perform. And this is just a simple sort of common sense exercise. If you imagine the hot air and the hot balloon that’s coming off your cooking it, it basically is going upwards. And if the hood doesn’t come out and cover that part of the cooktop, you can imagine that sort of hot air and plume and all the moisture and everything, it just goes in the kitchen and doesn’t get captured. It’s sort of a straightforward geometry thing. So if you can pick one that’s larger that that covers more of the cooktop area, that’s better. The other thing you’re deciding is what height to mount it at and you might think, well, the lower I get the better. Right? But that’s not always true. There’s sort of a range of mounting heights where we get reasonable performance. But you’re often going to be restricted by the cabinets that you choose also. And there are stock cabinet sizes that kind of limit your options there if you’re remodeling. But we usually want to aim for a height above the cooktop of something like 24 to 30 inches, if you will. That’s sort of measuring to the bottom of the hood. And it turns out that most modern kitchens with typical cabinetry, they’re going to have something in that sort of range.

Ian:                                    10:31                   If you’re using a microwave device, though, that that’s kind of different. The ones with the built in microwave tend to be mounted lower, for starters, and some of that simply because they are physically deeper top to bottom, right. If you’re mounting them under the same cabinet in your kitchen, it comes down lower. They also tend to not stick out very far and that means that they don’t have the greatest performance, honestly. And also they tend to suck air not just from underneath where the cooking is happening, but they often have vents around the top and the sides. And that’s what I would call more like general kitchen ventilation. So they are exhausting air but it’s from the kitchen, It’s not from directly over the cooking, So they’re less effective in that sense. So these microwave devices, sure you free up some counter space, but they are less effective as exhaust hoods for, for your cooking. Although I realize the popular in people liked them. So I would not say never install one, but you should understand that it’s not going to be quite as good as one that doesn’t have a microwave stuck in it.

Kelly:                                  11:35                   Just consider your alternatives in that case.

New Speaker:                  11:38                   Right. And the last thing is that there are some ratings for hoods that are put out by an organization called the home ventilating institute or HVI and anyone could go to and look at their ratings. And one of the key aspects of the ratings is to look at the the sound level, how noisy they are. Because in our research we found that as you can imagine, if a range hood is too noisy, people use it less particularly in a, in a modern kitchen, which has no wall between you and the dining room or living room. Like most modern homes are this open plan layout and the ferociously loud range hood, you can’t use it if you’re trying to watch television or the family’s trying to eat and have a conversation or something. It doesn’t work. Right. So you can try and look for quieter hoods. And in the future, those ratings are going to become a bit more advanced. And what they’re going to do is they’re going to start including something that we’re probably going to talk about for a couple of minutes here, which is something called capture efficiency, which is a rating for how well the cooking contaminants are captured and exhausted by the device. That’s not available yet. But a year from now when you’re shopping you should be able to pick a higher capture efficiency rated device also for exhausting your kitchen.

Kelly:                                  12:59                   Great. And can you dive into that a little bit? You’ve been doing some research on what the capture efficiency is of current range hoods. What does that look like from what you’ve seen in the market now?

Ian:                                    13:13                   Sure. So maybe I should define what we mean by capture efficiency first. Basically what capture efficiency is about is, when you emitting stuff from your cooking, what fraction of that get sucked into the range hood and blown directly to outside? So a poor range might say it only captures a third of all those cooking contaminants and it’s capture efficiency would be 33% or about a third. A very good range hood might capture 80 or 90%. So almost all of the cooking contaminants get sucked into the range hood and blown outside. And so capture efficiency is that rating that says how much of what I’m emitting from my cooking gets blown to outside. And we’ve done lots of experiments both in the laboratory at LBNL and also going out to people’s homes and testing, and there’s a huge range of performance for capture efficiency. And I touched on some of this earlier. It depends a bit on the geometry. You know, the physical dimensions of the hood in terms of how well it actually covers the cooktop. But as you listeners might imagine, often you have a switch that that changes the fan speed on your hood. And as you increase the fan speed, more and more air flows through it, the capture efficiency goes up. So you get the best capture efficiency at the highest flow rate. Unfortunately, that also tends to be the noisiest way to operate it. So there’s going to be a trade off in your kitchen, about how much noise can I stand. Generally the higher speed, the higher the airflow, the greater the noise and the better you will capture things. And at lower speeds, maybe you can still carry on a conversation, but it’s not capturing so well. And we have developed basically a standardized test method for this that is going to be adopted by HVI and other organizations so that everybody tests the same way. So that, you know, we standardize on things like what is the heat output of the burner that you’re looking at, and what method do you use to measure this capture efficiency and we’re using a tracer gas system for doing this. But it’s all in a very standardized, very controlled way. So all the test labs will get the same result if they test the same device in the same way. It’s all been engineered out to be very, very consistent. And theres several other test labs in the country that have been trying out this test method and also some European test labs also because we think that this way of rating for capture efficiency will probably find its way into international standards as well as being used here in the U.S.

Kelly:                                  16:03                   That’s great. So you’re working on that now. But can you talk a little bit about some of the other things that we can look for? You know, if I’m going to buy my range hood tomorrow, you spoke about noise and flow rate. What would you prescribe if I was going out and looking to pick something tomorrow?

Ian:                                    16:25                   If you’re picking something tomorrow, there’s sort of the minimum flow rate below which the devices don’t work particularly well. And some minimum flow rates are actually put into ventilation standards. For example, the U.S. National standard for ventilation says that the minimum flow rate should be 100 cubic feet per minute as a minimum flow rate. So if you’re looking at the flows that you’re going to get for your range hood you want to at least beat that minimum. Of course that’s the minimum, you can always do better. And if it was me picking a flow, I’d want to have at least 150, maybe 200 cfm as sort of the minimum flow rating that I would operate at. It’s a little complicated by the fact that almost all range of type of switch that lets you change the speed and change the flow, right? And on the very lowest flow, they might not be having that 100 cfm, but you probably get that on the medium. And then on the high flow rate you get up to 150 or 200 for a typical device. So you know, there’s always going to be a range of flows at the, at the more extreme end though for high end kitchens we see devices that are essentially looking at look like they should be in a commercial kitchen. Whether air flows are several CFM, maybe six, 700 cubic feet per minute. So like five times or six times what the minimum is. And that, that all seems like, hey, that should be awesome, right? Because now I’m going to get really good capture efficiency and all that sort of stuff, which could be true. But you pay a price in terms of noise for a start.These tend to be noisy to move all that air and the fact that all the air has to come into your house somewhere else, right? All the air that goes out comes in somewhere. And at the very high flow rates, that can be a difficult thing to manage for your home, and you can easily run into comfort issues. For example, if you lived somewhere cold and it’s winter time, all that extra cold air coming in has to be heated, which is, you know, going to cost you some energy. And if you have what we call makeup air, which has a deliberate duct to bring that air in, you have to be careful about where that air comes in. Because if you don’t heat it up in the winter, you get a horrible cold draft on people, so these very high end, very fancy higher flow devices bring a whole world of problems with them that currently the industry is not dealing with very well I would say. And it’s important when you’re picking these things to be aware that it’s not so simple as buying the biggest thing you can and turning it on, there are other consequences that we have to deal with when we do that, but that’s only for these very large, very high end devices. For your more typical thing that you might put in your kitchen, those higher air flows are less of a concern because they simply don’t move that much air.

Kelly:                                  19:22                   Right. Compared to the overall building size?

Ian:                                    19:24                   correct, yes. Well it’s not so much building size. It has to do with things like if you are living a very energy efficient home, they tend to be what we call very airtight homes. In other words, they don’t have very many leaks in the building to let air in or out. And if you have one of these very big exhaust fans, often they will actually move a lot less air than they say, cause it’s simply so hard to suck the air in through the very tight shell of the home. And sometimes we also have concerns about what about if you have a water heater in your house that takes its combustion air from your home? So this is not a sealed off unit. It’s not outside or in a garage or anything, It’s actually in the home with you, and that there are plenty of homes that have this, right. If you exhaust too much, you might pull the exhaust from the water heater into the house with you. So, you know, all of those combustion products that I talked about from the cooking, from your water heater, are coming in the house, which is, you know, water vapor and particles and, and carbon dioxide.All sorts of stuff. So there are some issues that we do have to think about if we install very, very large exhaust systems in homes that have what we call these natural draft combustion appliances in the home with them. I will say though that there are tests you can do to make sure that those devices are not overpowering the ability of your say water heater to draft properly. Organizations like the building performance institute and others have got, you know, test test protocols to, to evaluate this sort of thing. But, but again, I would argue for keeping your life simple and not buying a gigantic hood with a lot of flow, and going with something more moderate.

Kelly:                                  21:23                   Right. Yeah. And actually it’s interesting anecdotally obviously, but I’m up in Vermont this week and we have a lot of fireplaces and we actually had a situation the other night where the fireplace was running and somebody went into the bathroom and turned the fan on that’s integrated with the light switch. And there was a series of circumstances that made it such that we back drafted from the, the fireplace and smoke kind of came into the room.

Ian:                                    21:59                   Yes, it’s, it’s a real issue and it can happen and we should avoid it if we can. And again, I think this is an argument for using a more moderate airflow for your kitchen range hood if you can, and I realized that sometimes these are lifestyle decisions, not building science decisions and who am I to decide I can only, I can only advise people to avoid bad situations.

Kelly:                                  22:24                   Right. Of course. It’s one perspective of the whole construction game.

Ian:                                    22:29                   Well, I mean this is often the case when we talk about people’s homes is that a lot of the things in a home are inter-linked in these ways, right? The exhaust from the kitchen does great things to get rid of the contaminants in the kitchen, but we have to make sure we’re not messing up the home somewhere else.

Kelly:                                  22:48                   Right. That’s an excellent point. Thinking about that everything that you’re doing in the home as a full system. And what’s the impact on the whole system?

Ian:                                    22:57                   That’s right. Your house is a system is sort of a something we often say.

Kelly:                                  23:01                   And and were the building doctors or something

Ian:                                    23:06                   Possibly. And as any good doctor, we always have to firstly do no harm, right? We have to make sure that the things we do don’t end up making things worse. Right? But it’s a, it’s important thing but, but, but generally for most circumstances, you’re a moderately sized kitchen exhaust hood is not going to create very many problems in your home unless, and I s as I say, there are exceptions, but you know, some of this is becoming less and less important. This might be aside, but it’s certainly with thinking about, that most high-performance homes these days, they don’t have these gas fueled appliances that are actually using the air from the house. They’re either using what we call sealed combustion and most high efficiency furnaces. They’re taking their combustion air from outside through its own little duct.

Ian:                                    23:58                   It gets burned and then the flume goes back outside again. And that furnace isn’t communicating with your home in any way. And so it doesn’t really matter very much if you depressurize the house was an exhaust fan because that furnace is not communicating with the home. Or if you have a, an all electric home with say, heat pumps for heating and cooling and for hot water, then again, you don’t have to worry about it. But, but, but you crazy folks that want to burn wood in a fireplace. I mean there are solutions there too. I mean, again, in a high performance home, a good idea is to have what we call her a sealed fireplace. Where the fireplace is taking its combustion air from outside burning the word and then the, yeah, the smoke and everything goes back outside again and it’s not communicating with your home. And often these things will have, they have a, you know, a nice glass front on them so you can see the flames and the warmth comes through. But you couldn’t reach out your hand and touch the flames. But older homes, you know, like the one I live in, I don’t have that. I just have an open fireplace because I live in California so I can’t use it very often. But you know, you take your chances.

Kelly:                                  25:10                   Yeah, those are great points. Circling us back to the kitchen a little bit and cause I think that this is actually of interest to a lot of people. And not exactly kitchen hood exhaust but the cooker itself. So can you talk a little bit about our cooktop options and what your thoughts are on those?

Ian:                                    25:29                   Definitely. So, so they broadly fall into three categories if you want to do some cooking, right. There is a gas burner. There’s what we call an electric resistance element. That’s usually the spiral thing. You can see that glows red hot. And the third one is what’s called an induction cooktop where there’s nothing that gets hot and instead an induction field is induced in your metallic Cook Pot and the pot is heated directly rather than having gas be burned or a hot spiral element. And they are quite a bit different in terms of what happens when you turn them on. And the gas cooking is the one that produces the most contaminants because when you burn natural gas, you get a lot of water vapor which you need to control. There are also lots of particles generated, which are a health concern, oxides of nitrogen that again are a health concern and possibly some other volatile organic compounds that come from the combustion process. And so there’s more contaminants produced the gas cooking than the other ways. So the hot electric element is sort of halfway in between it. We’re not burning anything anymore. So we don’t actually produce any water vapor or oxides of nitrogen, but you never can get those heating elements so clean that they don’t admit some particles, and the particle emission is not as high as burning the natural gas, but there’s still plenty of small particles emitted when you use electric cooking. And finally the induction cooktop because effectively there isn’t something that’s super duper hot. You need heat to volatilize things to create the particles, it creates by far the least particles. It doesn’t create any water vapor, no oxides of nitrogen. So if you’re looking to cook in a healthy way that isn’t healthy because the food you’re cooking is healthy, but because you’re not putting contaminants in the air, an induction cooked up is definitely the way to go in all our testing and testing that other people have done, Induction cooking is definitely the cleanest. There is one other thing to think about though, and that is the oven and we don’t really have induction ovens per se, right? They usually either electric or gas and again, you sort of have the same breakdown where gas is going to produce the most particles and so on and, and the electric less so. They, they can be a little trickier when we’re thinking about venting. When we talk about the capture efficiency for hoods, we’re just looking at what happens on the cooktop. We’ve not looked at including in the rating what happens from the oven. And some of that is because the way the ovens are vented depends on a lot on the particular construction of the oven you’re using or the range that you’re using and where the hot air comes out. Sometimes it’s at the back, sometimes at the front, sometimes it’s a bit of both. And so it was sort of hard to standardize a way to think about capturing from the oven. But even if you’re not using the cooktop and you’re baking some bread or something, it’s still a good idea to turn on your exhaust hood because you’re still getting contaminants emitted into your kitchen. Maybe not as much as a very, very hot stir fry. Right? But they’re still there and you should still vent them. And maybe you just, you just leave it on low or something and do that. So it’s, it’s an important point to notice that, you know, when you’re cooking in the oven, things get emitted too, and the last thing I’ll say about this is sometimes in very, very fancy high end kitchens, you might have multiple ovens and maybe you have a cooktop with an oven underneath it with a hood over it. But on the wall next to it is a second oven. Well it’s not underneath the range hood anymore, but that’s okay because once again, turning your range hood on, it’s also ventilating the whole kitchen. Right. And it’s stopping the pollutants from traveling from your kitchen to other places in the home because as you exhaust out of the kitchen, the air has to come from somewhere and that airflow into the kitchen tends to control the transport of these contaminants around your house. And so even if what you’re doing isn’t directly under the hood, when you turn on the hood, you’re still sucking air out of the kitchen and ventilating the kitchen and moving those contaminants. It’s not as efficient as it is when it’s directly over the cook top, but it’s still something that’s worthwhile. And indeed, there are many other kitchen ventilation approaches that don’t use a range with per se. Right. Sometimes there’s just a fan in the wall or a fan in the ceiling that exhausts the whole room. And again, they work, they’re just not as efficient as a range hood and in order to get to the same levels of contaminants in the kitchen, if you just generally ventilating in the kitchen, you have to ventilate a lot more than if it’s just the range hood, and so those are less effective but it’s not like it has zero effect.

Kelly:                                  30:52                   Right. Great Point. Yeah. So thank you. There’s a lot of key takeaways here. I would say some of my top ones are number one, use your exhaust fan. Number two, vent it to the outside directly. And my number three is I should get an induction stove so I can make a bacon cheeseburger and call it healthy cooking.

Ian:                                    31:21                   I wouldn’t, I’m not sure I’m going to agree completely with your point number three about whether what you’re eating is healthy, but in terms of what you were emittnig and what you’re breathing. It might be slightly healthier. And, you know, I’m not against gas cooking, I cook with gas myself, right. But I use my range at a lot. And I understand that, that there are people that have, they love to cook and they have an affinity for using gas and I’m never going to tell them to not do it right. But I’m gonna tell them, you know, the air in your kitchen is going to have less contaminants if you use the induction, I mean I think my next cooktop will be induction even though I like to cook a lot.

Kelly:                                  32:03                   All right, good to know. So, we like to ask this, if we have you back on the podcast in five years, maybe 10 years, what will we be talking about then? Besides how awesome your induction cooktop is

Ian:                                    32:20                   I think we’ll be talking about a couple of things. I think that the design of range hoods is going to get better. And by that I mean we’ll get the same amount of the contaminants captured and exhausted from the kitchen at a lower air flow. And I like that because it means it’ll be quieter, which people are much more likely to use their hoods. And it means that if we move less air that’s less air we have to heat up or cool down, you know, that goes in and out of the house. And so that’s going to be something that I think we’re gonna see the range of manufacturers looking into. The next thing is, is, is automation, which is, you know, we made this point about range, that it only works if it’s turned on right. But once we have got good designs that capture well and arent noisy because they move less air or else theyre better aerodynamic designs, then I think we can move down the path of let’s automate these devices so they will sense that you’re cooking and turn on automatically and they’re likely to turn on at, at a low airflow and there’ll be a switch that you as the cook can still use. Like if you, if you start to burn something, you could turn it on to high. Right. But they’re gonna automatically operate. So it’s not dependent on, on the cook to turn it on. It’s going to be automatic. And the automation is an extension of, there are some high end hoods out now that have what I’ll call an emergency switch in them. If they get very, very hot, they’re intended to detect a cooktop fire and go into high speed. It’s a safety thing. And those controls strategies are going to get adapted to be more sensitive and use some different ways of sensing the cooking, not just the temperature of the air, but maybe some infrared sensing and things like that. And we’re gonna automate range hoods and I, and I think that sort of performance improvement and automation are going to be the two big changes that we see in sometime in the next five years. These things are going to become relatively mainstream.

Kelly:                                  34:25                   Okay. That sounds great. You did mention three things at first, do you have a third or are we going to have to wait and see?

Ian:                                    34:34                   There is a third one and this is something that may be a bit of a stretch and that is that there are some applications where people would like to recirculate. And the reason why I was gonna say it is third and then then I changed my mind is that I understand that with these devices you could certainly put in a good particle filter to move the particles. You could put some active charcoal carbon filters in there to remove some of the vcs, but youre still gonna have a hard time with removing the water vapor. Right. And that’s always gonna be an issue if you cook a lot, you know, and you don’t want condensation and we don’t want higher moisture levels in our homes. And it also has the issue of, it’s really relying on the homeowner to regularly change out all those filters. And from what we know from how people use their homes in particular, looking at how often people change the filters in the heating and cooling systems, we’re pretty sure we can’t rely on people to do that. So this, this is a third option and it’s being investigated mostly for like Super Duper, super tight homes where they want to keep the heat in. If you’re familiar with the, the passive house system where houses are very, very airtight and they are doing an amazing job of controlling all the heat flows. In the winter, they want to keep the cooking heat in the house as heat because they don’t want to turn on the heating system. And so they would like to have recirculating systems that allow them to do that. But I think there’s still, you know, a couple of really serious issues with those where I would be comfortable in recommending them. So they could be the third thing, and there’s certainly a bunch of work being done right now on how do we improve the filtration of these things. How good a filter do we need? And so on. But like I said, they have a couple of key drawbacks, which is they don’t remove the moisture and they do require a lot of maintenance. That means that- I won’t say they’re terrible, I’m just not their biggest fan.

Kelly:                                  36:41                   Right. That sounds great. So maybe we’ll put that on the 10 year horizon and we’ll check what they’ve got going on then

Ian:                                    36:49                   Maybe we’ll see. I just always prefer simpler things because they’re harder to break. Right. And you know, you want to buy something that’s gonna work for at least 10 years. And so the idea of, you know, robust things that don’t require you to maintain them all the time seem like they’re much, much more likely to be working in 10 years.

Kelly:                                  37:11                   That’s an excellent point and I think it is a good end note. So I want to thank you so much for your time today and for coming on the podcast and coordinating this remote recording with our team. Thank you so much Ian.

Ian:                                    37:27                   Well thank you Kelly. I’m happy to talk about these things as you can probably tell.

Kelly:                                  37:31                   Great. We’ll have you back on soon.

Ian:                                    37:35                   All right. Thanks, Kelly.

Robb:          Thanks for listening and thanks to Iain and Kelly. I mentioned at the start that I reached out to Ian about new developments on this front in the, you know, two, two and a half years since we recorded this episode. And he gave me a few interesting notes. One is that there really is growing interest in induction cooking both from a safety perspective and an electrification perspective for reducing CO2 emissions in homes. Also some new research shows that cooking with nonstick pans results in lower emissions, lower particulate emissions than with other cookware. California is considering codes that require higher ventilation for gas than for electric cooking, and this code may also include capture efficiency for range hoods. As Ian mentioned, there is an ASTM standard out there for assessing capture efficiency and range hoods, but this hasn’t yet caught on, if codes start to require it even as an option hopefully we should start to see some rated products. That’d be really cool and last but not least stay tuned for more on automatic raincoats that automatically operate when you start cooking. Iain had mentioned that there’s a lot of product development happening on this front. Buildings and beyond is produced by Steven Winter associates check us out at That’s Swinter.Com/Podcast is where the podcast episode lives and where the show notes live. Check out that page for some of the links I mentioned here, check out our careers page. If you’re interested in opportunities, we’re focused on making buildings better on all fronts, more healthy, efficient, accessible, resilient, affordable. The list goes on and on. We have offices in Washington, DC, Manhattan, Connecticut, and Boston. I counted 18 openings today on our careers page in most, if not all of our offices. So check that out if you’re interested and thanks to the podcast team here, Kelly Westby, of course, who did this interview, Heather Breslin, Jayd Alvarez, Alex Mirabile, Dylan Martello, and I’m Robb Aldrich. Thanks very much.

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