Getting Into the More Difficult Weeds on Decarbonization

September 27, 2022

Recently a friend asked me over to see if switching from his gas furnace to heat pumps would make sense—he’d gotten advice from one heat pump installer that his house wasn’t a good candidate, and also got a separate quote of over $60k for an elaborate heat pump system. Why can’t you just switch from a gas furnace to a heat pump?

Thermal Envelope

The thermal envelope, it turns out, really matters. The house in question is a poorly insulated, leaky house—in other words, sorry to say, a typical older house. Houses like that will have rapid changes in temperature inside with rapid changes and heavy winds outside, and require a lot of energy to heat and cool. Most gas furnaces are made to blow a lot of air and heat, so they can respond to sudden demands; but heat pumps are designed to hum along at a fairly even temperature, and don’t have the capacity to ramp up quickly. In other words, residential heat pumps do really well, and are most efficient, in buildings with decent-or-better thermal envelopes.

Courtesy buildingscience.com

Heating Capacity

The other simple problem is capacity: this house had an existing 8-ton heating system (about 100k BTUh) connected to big ducts. There is no 8-ton heat pump you could just plug in to switch from gas to efficient electricity—the biggest I know of is about 4 tons. So you would need to redesign the ducting system to break up the house into two smaller zones, and as you can imagine, complexity, expense, and disruption of the house would increase. The $60k+ quote he got was for—get this—3 outdoor heat pumps with EIGHT indoor units—linesets everywhere, lots of equipment to maintain, and, yeah, expensive. All to heat a poorly insulated house.

Retrofit

What to do– choose a bigger hose, or a bucket that doesn’t leak? This is a good case for insulating first: with insulation and air sealing, the heating load can be reduced drastically, often by 50% or more. This will require some expense and disruption on the house, but once you do it, you need less expensive (smaller) HVAC equipment, and you’ll spend less on heating and cooling forever– you will have locked in that efficiency for the life of the building.

The Expense Equation

Let’s not kid ourselves—the insulation job won’t be cheap either. To do it right means dealing with the roof—probably by spray foaming the underside of the roof deck to reduce stack effect and heat flow, get a few inches of the correct type of insulation on the existing foundation walls, and in this case, with a brick structure, consider putting exterior insulation over the brick with new siding over it. All of that will run in the neighborhood of $60k I should think, and then the HVAC system might now be down around 30k. Good news is there are many incentives out there to offset those costs—with new on top of existing federal incentives for efficiency upgrades, and a $10k retrofit incentive through our local village, the bill may come to more like $50k: less than the wasteful options, with way lower energy bills and a more comfortable house. Maybe I was guessing too low and the total may come out to around 70k after incentives—even so, there would be a tradeoff of lower energy bills for increased loan cost, maybe close to a wash.

Future Energy Costs?

None of the above even takes into account where energy prices are going. Almost as certain as death and taxes are rising energy costs. Between extreme weather, supply chain, and war in Ukraine, it’s been volatile lately, and my hunch is it’s not going to just quietly settle down quickly. To reduce energy use at home, especially with renewables and backup batteries, brings some peace of mind as well as lower bills. I would say it’s worth it.

Courtesy EIA.gov
Courtesy EIA.gov

Material Connection

September 1, 2021

One of the advantages of working closely with my friend and builder, Eric Barton (Biltmore Homes), on my own home renovation is the chance to literally get my hands on all the materials we’re using, and to discuss material techniques and strategies as we go. It’s not the textbook approach where the builder reads the plans and specs and installs exactly what the architect said; it’s the architect and builder looking at the crawlspace ceiling, scratching our heads, and asking, “how can we do this without spray foam?” That sort of thing.

During the August 25th Green Built Home Tour, I described the moment I had when we removed the gas line from our house as part of this project. I no longer had a pipe coming into the house with a gas that could catch on fire, kill me with carbon monoxide, and poison my family every time I cooked. Having it gone was surprisingly visceral. I’m getting the same with the materials.

What really struck me over the weekend while I was painting trim and installing foundation insulation was the emotional connection to material. When you cut wood trim, you get sawdust. Don’t breathe it in, but it has a nice wood smell; cut cement fiber board trim, and you should be afraid—you should fear the silicates that you really shouldn’t breathe in. Cutting wood fiberboard insulation, you make compost; it’s totally different from cutting EPS (Styrofoam), with horrible white plastic pellets littering the jobsite, impossible to contain. The list goes on and on, but the upshot is that we can and should build durable, beautiful buildings from non-toxic materials. Some are harder to get than others, but aside from current supply chain issues, they’re getting more available as the design and construction industry demand them. So keep demanding!

Another recent experience we had on a project was an attic spray foam job that continued to smell days after installation. If the spray doesn’t cure properly due to the mix or the temperature, the uncured or still curing material can smell bad and contain some toxicity. Also, according to an experienced foam installer I know, apparently supply chain issues in the chemical manufacturing of the foam components has resulted in some bad batches.

It seems that from the late 19th century to now, we have created and deployed so many toxic materials—lead, asbestos, PFAS, vinyl, benzene and other various petroleum by-products, coal ash with its heavy metals, microplastics… while right in front of us we have wood, cellulose, stone, adhesives without added formaldehyde, solar and wind power, and so on. Check out our resource document for products, documents, websites, and more.

A guiding quote by Frank Lloyd Wright: “Study Nature, love Nature, stay close to Nature. It will never fail you.” We don’t always have all the information we need on every material we get our hands on, but I will always be looking for those feel-good materials as close to Nature as possible. 

Eric Barton installing salvaged corrugated siding over Steico fiberboard

Decarbonization Renovation Flow Chart

July 19, 2021

Following up on the last post introducing the idea of decarbonizing existing buildings, this post features a flow chart that illustrates decision points and issues for decarbonizing homes in a cold climate. There is plenty of complexity in any building project, arguably more so in renovations; so this isn’t a how-to guide so much as a view into our thought process about the different facets of a project like this. We expect this to change as technology advances and we complete more projects of this type.

Please feel free to download our Decarbonization Resources with links to our recommended websites, products, and organizations:

Retrofits for Longevity: Health, Design, and Clean Energy

December 18, 2020

In the US most of our buildings are not optimized for indoor air quality, energy efficiency, or today’s living patterns. As our building stock ages, and as appliances and HVAC systems, windows, and finish surfaces reach the end of their service lives, we face an opportunity to radically upgrade: we can refashion our buildings toward a positive vision of the future.

Since the 1970s, researchers and the DOE have studied building science* to determine climate-specific recommendations for levels of airtightness and insulation, ventilation and conditioning systems, and efficient appliances. Following these best practices leads to more durable, comfortable, energy efficient environments with far greater air quality than is typical. These to me are the goals of all building, whether new or retrofit, and they can all be done while upgrading appearance and function. Even without going to extremes, houses in most of the US, including our Chicago climate, can achieve 75-100% energy use reduction while weaning off fossil fuels. All the technology and know-how we need is available right now.

To give a sense of the scale of the issue, consider the Chicago region: since we’re a cold climate, nearly half of residential energy use goes to heating. According to 2010 Chicago data, residences collectively use about 24 trillion kWh annually; if these used a sustainable 3,500kWh per person annually, that would be reduced to about 6 trillion—a factor of 4 reduction, while leaving fossil fuels behind. Most of the energy that goes to an older home, typically a leaky and poorly insulated building, is wasted; but with good retrofits, we can get there. I will demonstrate how in my 1919 house I achieved an 84% energy reduction in five steps, which also meant a 75% reduction in my required furnace (which becomes heat pump) capacity.

So what are the roadblocks? The first, as I see it, is lack of vision: it’s easy to remain entrenched in our old, fossil-fuel age, poorly ventilated mindset, and therefore extend our low level of performance. It takes some analysis and experimentation to get beyond that. In TBDA’s remodel and retrofit work we often chart a path to low- or zero-energy use for clients, with the understanding it doesn’t all have to be done at once; but the near-term steps shouldn’t hinder the long-term goal. You have to see down that path ahead, and knowing how each step is contributing to your big goal keeps the motivation high!

Another problematic-at-scale roadblock is the use of real estate for short-term profit. A flipper or developer doesn’t have incentive to do more than code minimum since they won’t get the financial or health benefits of a higher performing building. A production builder may lock in an inefficient thermal envelope and mechanical system for 25 to 50 years—and we only have 10 to get in front of catastrophic climate change. This will probably require demand, and either financial incentives, stricter regulations, or both.

Next, the question of cost: the knee-jerk reaction is that it costs substantially more to build at a higher level, but studies have countered that. True, a couple exhaust-only bath fans are cheaper than an energy recovery ventilation (ERV) system; lots of insulation costs more than little insulation in the short term. But when you look at life cycle costs and the health effects of the envelope, you may have a different value scale than the flipper or production builder. For new construction, the cost to build to a very high level of performance is, from our research and others we’ve seen, only in the 1-7% increase in initial building costs—easily justifiable by long-term energy savings and increased comfort and air quality. This small a margin is within the range of trade-offs for tile or countertop costs, or slightly reduced (better designed!) square footage. In retrofits the math can be harder, but sometimes forgiving, since you face the need to replace aging infrastructure like mechanical systems or windows. 

Thus far, each retrofit we’ve seen is unique, but themes and prototypes are emerging. In our next posts, we will be showing case studies to discuss the design and goal-setting processes, building science, energy modeling, and cost issues. In particular we will attempt to outline cost challenges where they occur so that policymakers can understand where incentives will be needed to get us on track. This is our decade to make a difference.

*Retrofit energy modeling begins at 3:07 of video above

** Resources include Deep Energy Retrofit Guidance from the Building America Solutions Center,  NREL’s Standard Work Specification website for home energy upgrades, Building Science Corporation’s trove of research papers, insights, and Joe Lstiburek’s wit, the Green Building Advisor website, PHIUS, Fine Homebuilding, Journal of Light Construction, and other publications.

How TBDA Uses Passive House To Design Better Buildings

December 6, 2019

Passive House is more than an energy standard—it’s a way of understanding the technology of high-performance building, and it allows architects to optimize a building’s performance through the design process, regardless of whether an owner wants to pursue certification or not.

The “business-as-usual” approach to design is to focus on program and appearance, then have an engineer or contractor size mechanical systems to condition the building; more sensitive designers may take into account sun angles and daylighting, but for many designers these are afterthoughts as well. That approach usually leads to needless energy consumption, glare, overheating, and thermal bridging. Our approach is to use the powerful Passive House modeling tool to tune the building to the climate as an integral part of the design process.

We begin design with an analysis of climate (temperatures, humidity, sun, rain/snow, wind), vistas and sense of prospect or “belonging” on the site, topography, and neighborhood or natural setting, all to allow the building to speak the language of the site. I think of it as imagining a living thing that evolved to live in that place—its feet or roots in the ground, its back to shelter, its face to the sun, with the right brows, whiskers, or foliage, as the metaphor may be!

That leads to initial gestural designs that become building shapes. As soon as we settle on a general layout, we then bring that geometry into our Passive House (PHIUS) modeling software (called WUFI-Passive), where we can enter values for insulation, window size, orientation, and performance, mechanical system performance, and internal energy use. By trying out different values for these, and by trying different approaches to shading and exposure, we can arrive at an optimal performance level for the building.

Part of the beauty of the PHIUS standard is that the climate-specific metrics give definite targets to design toward. When we optimize for both heating and cooling loads, we set the stage for comfort; when we minimize overall energy (efficient mechanical system, lighting, and appliances), we can design a project to meet annual net zero energy with the smallest solar PV array possible. And from a design point of view, we know the building will have a climatic “fit” that will allow the building to feel true to place.

If there’s one absolute I go by, it’s that Nature is right. I use the PHIUS tools and knowledge to allow my designs have an organic approach to energy, just as I employ biophilic design and understanding of the locality to allow the designs to have an organic, natural countenance and fit with the site. We’re pursuing ecological architecture through both art and science.

Tom Bassett-Dilley Architects | Contact