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Air-Source Heat Pumps in Homes: Step #2 – Pay Attention to the Envelope

This is part of a series; see the first post here.

This shouldn’t be news to anyone:  In most homes, insulation and air sealing are the most effective ways to improve comfort and reduce heating and cooling costs.

This holds true regardless of heating systems or fuels used. So why is it emphasized even more when talking about heat pumps and electrification? Four reasons.

1.  Heating System Capacity and Cost.

Say your home has a design heating load of 60,000 Btu/h.[1] If heating with fuel, you’ll need a furnace or boiler with a capacity of at least 60,000 Btu/h. These are easy to find. (In fact, you may have a hard time finding heating systems with capacities lower than this.) Air-source heat pumps, on the other hand, have smaller capacities. I don’t think you’ll find an ASHP with heating output of 60,000 Btu/h at cold winter temperatures. So to meet this load, you’ll need multiple ASHPs. And that gets pricey.

Even if you are not talking about multiple heat pumps, a 3-ton[2] heat pump is quite a bit less costly than a 5-ton heat pump. Costs of heat pumps scale more dramatically than costs of boilers and furnaces. So lower heating loads → fewer, smaller heat pumps → lower upfront costs.

Spray foam insulation

Spray foam in an attic – one of many ways to insulate and seal.


Air-Source Heat Pumps in Homes: Step #1 – Be clear about goals

This is part of a series; see the first post here.

Building new homes that are all electric makes TONS of sense. I’ve written about that before. Electrifying existing single-family homes, however, is not necessarily straightforward. Many state and utility programs in the Northeast[1] offer hefty incentives for air-source heat pumps (ASHPs), but fuel-fired systems are often left in place and used as the primary heating system. Clearly, when that’s the case, carbon emissions are not reduced much. Other programs are pushing completely electrifying homes and removing fossil fuels, but these programs are not gaining all that much traction.

This may seem obvious, but it’s important to consider homeowners’ goals and desires when installing heat pumps in homes. I don’t necessarily see this considered by policy makers and electrification programs, and I think it’s a big disconnect. Programs and policies are focused on the big picture (appropriately) and generally want to reduce/eliminate fossil fuels to help meet carbon reduction goals. What homeowners want can vary like crazy.


Air-Source Heat Pumps in Homes: Soup to Nuts

As I’ve written in several posts [1], electrification is all the rage. Modern air-source heat pumps (ASHPs) are fantastic technologies, and they can provide reliable, efficient, clean, affordable, and sustainable heating and cooling when done well and in the right application. I worry that these caveats are too often glossed over. I’ve also seen really bad heat pump installations, and I think it’s easier to screw up a heat pump than a boiler or furnace.

ASHPs on the exterior of a home

Three ASHPs at a home

This post is an overview of the process I suggest for good ASHP installations. I’ll be doing a post for each of the steps here, but this first post is an outline of the whole process because I believe the whole process is really important. The focus here is on homes, mainly in colder climates, and I’m not talking about VRF systems. I use the generic second person, so “you”  can refer to different people in different steps.


Electrification Nation with Laura Tajima

Cities across North America are paving the way for wide-spread building electrification. Although there are many benefits associated with going all-electric, there are also many barriers that stand in the way.

Building Electrification Institute acts as resource for cities in their equitable transition to building electrification through education, training, and program support. They work with 11 different cities, providing them with the necessary “tools in their toolbox” to ensure their buildings are as energy efficient, healthy, equitable, and cost effective as they need to be.

In this episode, our host Robb and guest Laura talk about electrification strategies, costs, and the importance of policy as it relates to building electrification and climate goals in cities.


It’s Time to 86 Fossil Fuels in Commercial Kitchens with Chris Galarza

Imagine this: you’re a chef or cook in a high-stress commercial kitchen setting. You’re making split second decisions with little breathing room, and each quick decision can get you cut or burned. On top of that, you’re in over 100-degree heat, breathing in toxic air from your gas stovetop.

This is an experience Chris Galarza could relate to, from working as a professional chef in various commercial settings. After making the switch to an all-electric kitchen utilizing induction equipment at Chatham University’s Eden Hall campus (the World’s first fully self-sustained university campus), he witnessed the positive difference in the physical and mental health of himself and his staff. He now advocates for electric cooking being a much healthier, safer, cost-effective, and energy efficient option.

In this episode, Kelly and Chris talk through some electric-kitchen-myth-busting, and ultimately answer the question “is moving away from gas and fire in the kitchen really that radical an idea or does it just make perfect sense?”


NYC Building Energy Letter Grades: What Property Managers Need to Know

Building energy efficiency labels are now available for property owners of large NYC buildings to download and post in their lobbies. Each year, the labels will be available on October 1st and must be posted by October 31st. Failure to display the label for applicable buildings by the October 31st deadline will result in a violation from the Department of Buildings and fine of $1,250.


Electrifying Central Ventilation Systems in Multifamily Buildings

A common strategy to provide ventilation in multifamily buildings is to design a central roof-top air handler that distributes outdoor air to each unit. The energy cost for this system, which commonly uses natural gas for heating for either a gas furnace unit or hot water from a central boiler is paid for by the building owner. However, there is another option – VRF[1]. With the unprecedented rise of VRF technology in the last decade combined with regulations such as New York City’s Local Law 97 of 2019[2] (carbon emission penalty), the industry is taking a giant leap towards building electrification. There are always questions and concerns raised against building electrification ranging from initial cost to operating cost to reliability of the VRF technology. From the owner’s perspective, the biggest question is usually surrounding the operating cost of an electric system compared to a natural gas system for heating, but the cost of ownership must consider multiple energy metrics. I was curious to understand the impact on various building energy profile metrics associated with a Dedicated Outdoor Air System (DOAS) using the conventional gas fuel source vs. the latest VRF heat pump technology using electricity in a multifamily building. The findings of this investigation challenge the deep-rooted notion that electricity, being more expensive than natural gas per BTU, will always cost more to operate.


Net Zero and Electrification

Net zero” can mean a lot of different things depending on what you choose to measure – zero energy usage, zero carbon emitted, zero lifecycle impact, etc.

At Steven Winter Associates, Inc. (SWA), we work with clients who are approaching net zero from different angles: driven by institutional goals, climate concerns, marketing campaigns, and connecting with municipal emissions targets. One thing we see over and over is that super high performance is difficult to achieve, but with a key simplification – there are not many ways to do it. All roads may lead to Rome but the closer you get, the fewer roads there are to take.


Electrify Everything? Part 1

So in utility and policy circles, electrification is all the rage. Grid electricity is getting cleaner (i.e. resulting in lower CO2 emissions), on-site renewables are taking off (sometimes even with storage), and heat pump technologies are getting better. More regional and utility initiatives are encouraging building owners/designers/developers to forego onsite fossil fuels entirely (or at least mostly) to help meet CO2 emission reduction goals. But is electricity really more sustainable than natural gas? Is it cheaper? Which is better, really?