CRES Northern Colorado Chapter
Are energy savings, beauty, and occupant health complimentary objectives or do they require trade-offs? At any rate, what does it take to achieve them?
“You basically want to think about your building as the third skin around yourself, the second skin being your clothes.” – Enrico Bonilauri, Co-Founder and Chief Product Officer, Emu Systems, Denver, CO
Our guest speaker at the September 28 NCRES Meetup was Enrico Bonilauri of Emu Systems, a Passive House training and energy efficiency consulting firm based in Denver. An architect with masters degrees in Architecture and Design Science, Bonilauri addressed how building standards impact human health. All non-attributed quotes are his.
Compensation vs. Conservation
When it comes to reducing a building’s net energy consumption, there are two basic strategies: Conservation and Compensation.
- With compensation you’re offsetting the building’s energy use with onsite or offsite production of clean energy. The most obvious example of this strategy is purchasing renewable energy credits or adding rooftop solar to a code-built home or office building.
- Conservation, by contrast, involves using building techniques and materials that reduce the need for energy to heat, cool, and illuminate a building in the first place. These are, for the most part, passive techniques.
Bonilauri points out that architectural and building techniques can easily result in a 75 percent reduction of heating and cooling energy requirements compared to code-built homes. In some cases, these are low-hanging fruits that have little to no effect on a builder’s budget.
It’s true that investing in clean power generation is essential to achieving net zero energy in buildings, but thinking in terms of compensation before conservation is putting the cart before the horse. It also ignores the health angle.
“Buildings are for people”
Many would argue that building features, materials and standards that improve people’s health and comfort provide a more compelling measure of value than energy savings. Fortunately, energy savings and occupant comfort are complimentary objectives. Good indoor air quality, even indoor temperatures, daylighting and minimizing ambient noise all benefit occupant health. What does it take to achieve them?
Mostly, it requires focusing on the building’s envelope.
- A building envelope includes the exterior walls, roof or ceiling, exterior windows, foundation, and bottom floor. Basically, it’s any part of a conditioned space that’s exposed to the elements.
Cornerstones of healthy, durable buildings:
- Well-insulated (high R-value), airtight building envelope with high-performance windows.
- Good ventilation system/strategy.
- Paints and finishes that are low in volatile organic compounds so they don’t negatively impact air quality.
- Strategically placed windows that provide lighting without increasing heating and cooling requirements.
By building a robust envelope and observing passive solar principals, you can achieve greater energy savings than what you might achieve with a compensation strategy. In a nutshell, it’s a demand-side approach to energy savings. It’s a passive strategy, in that it relies on building design and materials, rather than an active strategy relying on clean energy generation.
Insulation and thermal bridging
You may love the sight of icicles hanging over a porch after a snowstorm, but they’re a dead giveaway for a poorly-insulated attic. Patches of melted snow on a roof or condensation on the side of a building indicate where heat is escaping from a building.
- Thermal bridges refer to heat transfer through studs and other breaks in the insulation of a building envelope.
Good insulation keeps homes warm in the winter and cool in the summer. It attenuates, or reduces sound. A good envelope also allows you to save on heating and cooling systems, for instance by reducing or eliminating the need for air ducts. If a building has insulation gaps, however, this strategy falls apart.
Gaps in insulation are the devil. Thermal bridges degrades the performance of surrounding insulation, regardless of how robust it is. Even high R-value insulation has little effect if there’s a break every two feet where a stud has been placed.
“I don’t see high performance without avoiding this kind of situations”
Similarly, flimsy windows and doors are in effect holes in a building’s envelope. This point is key: Local temperatures surrounding windows and doors should be consistent with the rest of the building. A person is sitting near a single-pane window will adjust the temperature of the entire room to make that spot comfortable.
Bonilauri has measured localized temperatures as low as 17.6 degrees inside a brand new window. (I have the infrared image to prove it, in case)
“I had never seen ice forming on the inside of a window and then I came to Colorado and there it was.”
I’ve heard Brian Dunbar at the Institute for the Built Environment and others in the high-performance building industry liken homes with thermal breaks and cheap windows to leaky boats. It doesn’t matter how sturdy the rest of your boat is, if you’ve got a hole in it at the water line it’s going to compromise everything else. Building codes don’t address these issues effectively.
“If you sit right next to something that’s 17 degrees it’s like sitting right next to your freezer.”
This matters not only due to heat transfer but also because it increases the risk of mold and rot issues.
Indoor air quality: Do walls need to breathe?
If you like sleeping with your bedroom window open in the summer, you’ve probably been frustrated lately by the crud in the air spreading from forest fires in California and Utah. Opening a window for a while can stale or musty indoor air but allows outdoor sources of pollution to enter a building. It’s a bit of a conundrum.
Construction materials can release formaldehydes and other pollutants, and so can we. Our cooking and our bodies produce waste and if it stagnates or is recirculated within a building that affects occupant health. Airtight construction means air and moisture can be trapped and recirculated within a building, which is bad. All these indoor air quality issues give rise to this stupid idea in the building industry that “walls need to breathe.”
This idea, however, is folly for several reasons. Pushing warm and moist air through a leaky wall causes condensation, which leads to mold and rot. “If you have a combination of cold spots and high relative humidity, you have condensation and mold,” Bonilauri warns.
Both internal and external air pollutants need to be filtered. Here’s the good news: You can have your cake and eat it too — you just need an ERV.
- ERVs — energy recovery ventilators — exchange stale, indoor air for fresh, filtered outdoor air. ERVs and HRVs (heat recovery ventilators) provide a much more efficient exchange than conventional HVAC systems, maintain a comfortable temperature and don’t dry out buildings.
In effect, these systems act as a building’s lungs.
So no, walls don’t need to breathe. ERVs can also prevent moisture loss, eliminating the need for a humidifier.
Airtightness and building durability
This point bears repeating: Airtightness without a suitable ventilation strategy can cause issues including:
- loss in performance
- biological decay (rot)
“The more that buildings become airtight and energy efficient the more of a problem these issues become.”
This is a risk not only with new construction but with retrofits. Deep energy retrofits have lead to mold issues by trapping air and moisture. When measures are taken to improve airtightness and insulation, ventilation strategy must also be taken into account.
It’s never too late!
All these principles also apply to retrofits. Bonilauri cited a retrofit in Frankfurt Germany that resulted in 94 percent reduction in heating and cooling demand. Closer to home, the recent Empire State Building retrofit (which Rocky Mountain Institute was involved with) quickly paid for itself by dramatically reducing the building’s energy costs.
What value do I look for in a car?
We would never accept the same defects in cars as we do in buildings, but as Bonilauri points out, “There’s a casual assumption that buildings are going to be crappy anyway.”
What Value Do I Look For in a Building?
Put simply, building code only requires running water, structural integrity, and that building keeps (most) rain snow and wind out. Builders, property managers and building occupants should identify what’s important to them beyond code requirements: resiliency, indoor air quality, daylighting, and so forth.
“Ask yourself: Is healthcare going to get any cheaper anytime soon in the U.S.?”
The common cold costs a typical household $16K over 10 years. Asthma can cost $40K over 10 years. Mold and other indoor pollutants exacerbate these and other health issues.
“There’s no such thing as renewable health.”
The expectation that buildings are going to have quality issues — leakiness, mold, ice damming, uneven indoor temperatures, noisy HVAC systems — is part of our culture. Are we talking enough about how the built environment impacts our health? Is this the big, missing piece—or at least one missing piece—in the national healthcare debate?