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Posts by Srikanth Puttagunta

It’s Time to Focus on Our Schools

If you are a parent like me, I am sure you cherish your kids and seek to offer them the best opportunities in life. I even moved to a different school district. And, while the education is top-notch in my town, I have come to realize that it really doesn’t matter what school district you are in…all our schools need help. I am not talking about smaller class sizes, better pay for teachers, after-school programs, and more school supplies, although those are important. School buildings need attention. With budgetary pressures, a lot of maintenance and repairs are being deferred and schools are not aging well. Whether it is repairing existing systems, replacing systems at the end of their useful life, renovating, or building a brand-new school to service your community for future generations, advocate for your Board of Education (BoE) to think holistically about improving the conditions for our children.

Why My Call to Action?

This year I was asked to join our elementary school’s Tools for Schools committee, which is tasked with implementing an indoor air quality (IAQ) management plan. This experience gave me an opportunity to get involved and provided me insight into the school’s systems and the operations and maintenance (O&M) processes that were in place.

Unfortunately, at the start of the 2018 school year, mold issues were identified in our local middle school and the building was closed. In fairness, I quickly realized that buildings were outside the BoE members’ knowledge base. Afterall, they are educators, not facility managers or building scientists. They sought outside consultants but didn’t know the right questions to ask. After some time, the BoE decided to get input from local experts in the community. Fortunately, we have several experts (including me) who were willing to volunteer their time. As part of a task force, we laid out a strategy to remediate the mold issues in the school and to implement short- and long-term repairs to minimize/eliminate water incursion and elevated moisture issues within the building.

I am not saying you must get involved at this level, but I do encourage you to attend a BoE meeting and start asking questions related to IAQ. Ask if the school has deferred maintenance needs and if/when these are being addressed in the annual budget. Ask when (if) comprehensive physical needs assessments and energy audits were performed on all school buildings. Educate yourselves; then help educate your BoE and your community on IAQ guidelines for schools. Here are some great resources:

How Can SWA Help?

In working with schools, I have learned that one of the greatest challenges school decision-makers face is not knowing where to turn for support and guidance. Steven Winter Associates, Inc. (SWA) has been working to improve educational facilities for decades. Whether you have questions related to mold, moisture, comfort, absenteeism, accessibility, high utility bills…on up to zero energy design and progressive learning environments, SWA can support you. Here is just a sample of past school projects that SWA has worked on:

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Does Your Exhaust Fan Suck? Part 2

If you recall from Part 1 of this article written back in September, we discussed why exhaust fans often don’t operate as they are intended. Now, let’s discuss how to rectify these issues. First, we need to understand that all fans are not created equal. To do this, SWA participated in a “blind” study that analyzed a number of today’s common exhaust fans. The study emphasizes the importance of fan selection. With this understanding, we will then discuss solutions and best practices for installing bathroom exhaust ventilation.

The “Blind” Study

To get a comprehensive performance dataset for a number of exhaust fans, the Riverside Energy Efficiency Laboratory (REEL) was engaged for a “blind” study. REEL is the HVI/ESTAR neutral, third-party testing facility. In total, 7 multi-speed fans, 7 single speed fans, and 6 low-profile fans from six manufacturers were sent to REEL without manufacturer markings. In general, ten-point airflow tests were conducted on each fan. Testing adhered to standards used in the industry, namely, ANSI/AMCA Standard 210 and HVI Publications 916 and 920, where applicable. While the dataset is extensive, this paper focuses on the 50, 80, and 110 cfm ventilation rates, as these are the most common specified fan speeds for bathrooms. These fan curves show the relationship of airflow that will be delivered at various static pressures of the duct system.

Figure 1 shows fan curves for single speed fans that were tested. The units are rated for 80 cfm unless noted otherwise in the legend (two are rated for 70 cfm and one for 90 cfm). While all of these fans performed in a similar manner, would it surprise you that two of the fan curves in Figure 1 are for exhaust fans that use DC motors? People often assume that all fans using DC motors are the same and result in constant airflow for a range of static pressures (let’s say up to 0.4” w.g.).

Figure 1

Figure 1. Performance Data for Single Speed Exhaust Fans

It is clear in this data (Figure 1) that flow rates decrease rapidly when static pressure rises over 0.3” w.g., as it often does in real world installations. Oh, are you still wondering which two fans have DC motors? It is actually SS-05 and SS-06. A bit surprising, isn’t it?

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Does Your Exhaust Fan Suck? Part 1

You most likely don’t even think about it when using the bathroom. Flip the switch, hear the exhaust fan, and everything is working as it is intended…right? Far too often, the answer is NO, and it is no fault of the user. Sure, homeowners should take a minute each year to vacuum the inside of the exhaust fan housing, but otherwise, these fans should just work. So why don’t they? Hint…it all depends on how it was sized and installed.

Background

The purpose of exhaust ventilation is to remove contaminants (including moisture) that can compromise health, comfort, and durability. Exhaust fans are amongst the simplest mechanical systems in your home, but decades of experience working in homes has shown us that even the easiest things can get screwed up. Far too often, exhaust fans rated for 50 or 80 cubic feet per minute (cfm) of air removal are actually operating at less than 20 cfm. In theory, the exhaust fan should be installed in a suitable location and then ducted to the outside via the most direct path possible. However, the installation of an exhaust fan can involve up to three trades: an electrician typically installs and wires the unit; an HVAC contractor supplies the ductwork; and, the builder/sider/roofer may install the end cap termination. What could go wrong?

As energy efficiency standards and construction techniques have improved over time, new and retrofitted buildings have become more and more air-tight. If not properly addressed, this air-tightness can lead to moisture issues. Quickly removing moisture generated from showers is a key component of any moisture management strategy. While manufacturers have made significant advancements in the performance, durability, and controls of exhaust fans, these improvements can all be side-stepped by a poor installation.

So how do you correct this issue? (more…)

Trying to Be Rational in an Irrational World

Think about the last time you went looking for a new car. What did you look for? I am guessing you started with your needs for a vehicle. Are you looking for a large car/SUV to move a lot of people or equipment, a car for commuting to work, or something to enjoy on the weekends? Next you probably were interested in the looks of the vehicle because it is a large investment and you should like what you drive. I am guessing you glanced at the miles per gallon (mpg) of the car. You even likely went online to see reviews from others on the comfort, crash test rating, and typical maintenance issues of the car. Of course, you will need to look at the sticker price. I am even assuming you asked to test drive the vehicle to make sure that the information that you obtained aligns with how you perceive the vehicle.

Image of animated home Now, what if I told you that you must make that vehicle purchase decision only based on the dimensions of the car, the features (radio, A/C, seat controls, etc.) of the car, some pictures of the interior, and the price. Do you think you could decide on which car you would want? My guess is that you would say I am crazy and that you wouldn’t make the decision on such a pricey purchase with so little information. But, that is exactly what millions of people do when making a significantly more expensive purchase… a home.

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How Effective is that Range Hood?

Next time you are cooking, take a look at your kitchen hood. You are likely cooking on the front two burners, but your kitchen hood is not likely to extend fully over these burners. For typical exhaust fans, they do a good job of exhausting steam, contaminants, etc. from directly below them, but don’t necessarily pull all fumes that are outside the perimeter of the fan enclosure.  According to Lawrence Berkeley National Laboratory (LBNL) the capture efficiency of standard hoods is typically in the range of 30-40% on front burners and can be as high as 90% on back burners. To demonstrate this, I boiled some water in a tea pot on my stove. Once steam was coming out, I pulled out an infrared camera and started to take images. Wait…you don’t have an IR camera just sitting around your home? You are missing out on hours and hours of fun with the kids. They are great for science projects.

Back to my point. I have an LG over-the-range microwave with extenda™ vent. This allows the vent area to extend out an additional ~6”. When the microwave hood (exhausted to outside) was operating on turbo mode (just over 300 cfm exhaust) and without the vent extension slid out, the majority of steam from the tea pot on the front burner was passing by the vent and going up the front of the microwave (as evidenced by moisture build up on the microwave door). And yes, I realize that I turned the spout of the tea pot outwards to more dramatically show the point I am trying to make. When the slide out vent was pulled out, the amount of steam capture increased dramatically, but there was still some moisture build up on the front edge of the vent slide out.  Obviously, this is not a scientific study; it is just anecdotal evidence to further the discussion on the need to consider capture efficiency in the design of kitchen range hoods.

Infared_Collage

Figure 1. (Left) IR image of steam from a tea pot bypassing vent hood without hood extension slide out. (Center) Picture of range and hood setup with hood extension slide out. (Right) IR image of steam from a tea pot mostly being captured by vent hood with hood extension slide out.

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When Did Building Science Become Energy Efficiency?

If nothing else, people are adaptable. While something might be an annoyance at first, we often figure out a way to manage it and move on. Unfortunately, we all too often do this when it comes to our greatest life investment…our homes. Whether an existing or new home, we almost always are not comfortable in our home or at least portions of our home. One, several, or even the entire home may never be at desirable conditions, but we learn to cope with it by putting on layers of clothing or adding small electric heaters to cold spaces, or supplemental fans in hot ones. So we are not comfortable as we allow our conditioned air to easily escape our homes and our utility bills continue to be high. The simple question is…why?

Mike Trolle

“People have all sorts of misconceptions about the sacrifices that they feel they have to make in high performance homes and it is completely untrue. It is exactly the opposite. The even temperatures, the lack of drafts, the feeling of warmth, comfort, and right levels of humidity and fresh air…they are unrivaled. Comfort is something you have never experienced properly in a home until you have a high performance home.” – Michael Trolle, BPC Green Builders
(Source: CT Zero Energy Challenge 2012)

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Please Turn on the Fan

I love to cook. And like most cooks, I love to cook on my gas range. But I am also a building science researcher, and the researcher in me doesn’t understand how we allow gas ranges in homes. Building codes and energy efficiency programs have pushed the housing market towards all combustion appliances being sealed combustion and direct vent. Our furnaces, boilers, water heaters, and fireplaces are all going towards sealed combustion. Soon it is likely that building codes won’t even give you the option of using open combustion devices. This push for sealed combustion is an effort to drastically reduce the health hazards of carbon monoxide poisoning and other contaminants in our homes. As a researcher, this makes complete sense to me…but I, like many others, say “Don’t touch my gas range.”

Measuring Carbon Monoxide

My colleague, Steve Klocke, testing the carbon monoxide from his beautiful range.

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Air Sealing with Open Cell Spray Foam Insulation – Know the Risks

As the latest versions (2012 and 2015) of the International Energy Conservation Codes (IECC) push for more efficient homes, we are getting more questions from architects on how to achieve the air tightness requirements of 3 ACH50. There is no one correct answer, but it can be often achieved through taping of exterior structural or insulated sheathing, air sealing of wall cavities prior to insulating, and/or the use of insulation that is restrictive of air movement. The most common approach that we are asked about is the use of open cell spray polyurethane foam (ocSPF), as it is air impermeable (required thickness is dependent on the specific product, so check requirements in the ICC Evaluation Services Report), reasonably priced, and theoretically, doesn’t require any changes to standard builder practices. While it is true that ocSPF will provide air sealing cost-effectively, we typically do not recommend it in our cold climate region without additional measures due to risk potential over time. To effectively build a home with ocSPF, thoughtful detailing and a high level of execution is required to ensure that it remains effective 5, 10, 15…25 years from now.

ocSFP Window Flashing

While this wall assembly was not insulated with ocSPF, poor window flashing details are a common issue that we see and is one of the reasons we are cautious with this insulation approach.

  • ocSPF is vapor permeable, so there is a greater potential for condensation in the building enclosure than if closed cell spray polyurethane foam (ccSPF) is used. A hybrid approach of ccSPF and an alterative insulation (ocSPF, cellulose, fiberglass, etc.) is often used to keep costs down.
  • ocSPF can absorb 40% of water by volume. Therefore, if bulk water from leaks does make it into the building enclosure, the ocSPF will retain the water until saturated. Pinpointing the source of the leak may be difficult as the water can migrate within the foam.

Our main concern is that the performance of the product requires several trades to meet a high level of quality to ensure success and hope that the homeowners don’t unwittingly cause problems down the road through lack of maintenance. Here’s what we suggest…  (more…)

The $300 Investment Every New Construction Home Should Make

Whether code built or energy efficient, if your new home has a poured concrete foundation and floor slab, please pay particular attention to the following. While older, leaky homes result in low interior moisture levels (thus the desire for humidifiers on central furnaces); newer, tighter homes will typically have relative humidity levels in the 25-50% range naturally.

Window

Moisture from construction materials in new homes must be managed to avoid problems like interior condensation and mold.

In some cases, there is a need to actually dehumidify to maintain relative humidity below 50% during the winter. In the first 1-2 years after the home is built, concrete foundations expel massive amounts of moisture as part of the concrete curing process called “hydration”. As the concrete cures, some of the water in the concrete mix reacts chemically with the portland cement and forms the hardened concrete, and some of the water evaporates to the surrounding air. The exterior water resistant/proof coating on the below grade portion of the foundation prevents moisture from escaping that way. Typically only a 1-2 foot tall area along the perimeter of the above-grade portion of the foundation is available for drying to the exterior.  It is more likely that the moisture will be expelled to the interior of the home and therefore, must be managed to prevent deleterious moisture-related problems such as condensation, mold, wood rot, etc.  Framing lumber also contributes: lumber that starts out kiln-dried at 18% moisture levels, will eventually end up at 6%.

How to deal with that moisture? Here is that cheap investment alluded to: an ENERGY STAR dehumidifier with a built-in humidistat.  This unit should be plumbed to a drain to allow continual operation (without having the occupants empty a bucket).  In addition, the dehumidifier should be installed in the basement or crawlspace as soon as the structure has been enclosed and power is available. In terms of the construction process, it is recommended that the foundation be the last item to be insulated to allow for the internal construction moisture to be removed prior to enclosing. After a year or two of occupancy, construction material moisture levels will become stabilized at “normal” levels. In the interim, remember to “build-tight and ventilate right”, but also manage that construction moisture.