As a building material company, we attend some pretty cool industry conferences. These are typically in-depth events designed for trade professionals like architects, builders, and designers. We often remark that homeowners should attend one of these to learn about the avant-garde of building trends. This is especially true for the sub-segment of sustainable building given its constantly changing landscape and the difficulty discerning true trends from fads.
Last week we attended NESEA’s BuildingEnergy conference in Boston which had many discussions that any current or future homeowner would benefit from. One particular presentation on Deep Energy Retrofits (DER’s) struck us as almost mandatory for anyone contemplating a serious home renovation.
The Background
A Deep Energy Retrofit refers to the process of significantly improving a home’s building envelope and onsite energy use through a holistic approach. It’s not isolated to just one system or section of a home. Typically a DER will include an overhaul of all (or nearly all) energy loads — space conditioning, hot water, lighting, appliances, and plug loads. It will also likely include improving the entire building envelope, ie super insulating. Adding passive solar design and renewable energy systems is also common. If you’re living in an old, leaky house that uses a lot of fossil fuels many architects and builders will recommend a Deep Energy Retrofit.
The rationale behind a DER seems sensible but such a large project is expensive and often requires replacing existing systems and materials that may still have useful life in them. This can add a lot of embodied carbon to the project which, as we’ve written about before, is just as important as operational carbon in addressing a home’s overall carbon footprint. So a DER will definitely reduce energy consumption but with costs that challenge its feasibility and scalability.
Another Approach – Moderate Energy Retrofit
So if you can’t afford a DER (like most people!) and Embodied Carbon matters to you (like it should!) there is a solution. And like most solutions to difficult problems, it’s pretty simple.
A Moderate Energy Retrofit (MER) can significantly improve your home’s energy efficiency while reducing Embodied Carbon and not breaking the bank. The focus shifts from super insulating the home to the electrification of heating and cooling systems. A whole house envelope upgrade isn’t necessarily a precondition to installing new heat pumps. Air tightness still matters and a MER will show significant improvements on a blower door test but it might not be enough to brag about.. 5.0ACH50 vs 0.5ACH50! Instead of replacing all windows, only replace the worst ones. Make sure to do the obvious (and inexpensive) air sealing like your basement rim joists. Addressing other areas of fossil fuel consumption like hot water can also be part of a MER.
What Does the Data Tell US – MER vs DER
One single-family home example cited at the conference gave some compelling data.
A MER can reduce the amount of annual carbon emissions of a home by 74%. A DER will do more, likely over 90% but 74% is still pretty impressive.
The heating load can be cut by more than 50% and annual site energy usage reduces by 75%. Again DER does more but the efficiency gains are still there.
The upfront embodied carbon (without storage) was ~4,000 kgCO2e vs 12,000 for a DER.
Upgrading of mechanical systems is pretty similar but the building envelope upgrade of a MER was less than $50k vs a proposed $200k with a DER.
So to conclude, a MER achieves massive improvements in your home’s energy consumption and fossil fuel usage while using much less carbon and your hard-earned money.
Moving Forward
If we are going to meet our climate goals, we need to address carbon in our existing housing stock. But we need to do it in a scalable way. A $200k renovation is just not a solution for most people. We also need to emphasize the role of upfront embodied carbon. Using carbon-intensive materials to super insulate a home can actually move us backward. So if you are looking at a home renovation, please keep these dynamics in mind. It may just turn out that you don’t need to bankrupt yourself to help save the planet.
Also, this historically opaque conversation is becoming clearer. A few resources to consider:
Note: the first two were created with the sole intention of helping homeowners actually achieve their goals related to MER or DER. These challenges are indeed getting easier!
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