14 Design don'ts for high performance homes
There are a lot of ways to design a home. Designing one for high performance, though, or even better-than-average performance, has many recommended best practices that are based on a lot of research of homes that have failed because they're unhealthy, inefficient, and/or falling apart.
This is why we have building scientists (see SOAP BOX below); to provides us with the Do's and Don'ts of designing high performance homes.
Here are just fourteen Don'ts that are too often Do's that lead to homes with high energy use, bad indoor air quality, sick people, crumbling buildings, or ugliness.
1. fill up all the walls with windows or leave exposed windows un-shaded. No matter how "super efficient" they are, windows are poor insulators and they can let a lot of the sun's heat in to a home.
2. put a vapor barrier in the walls, floors or roofs, or anywhere else other than underneath the slab or crawlspace floor. This will lead to trapped moisture in failed building assemblies. It's only in climate zones 7 and 8 that you might consider using one, but you'd better be sure.
3. let the water in. This is possibly the most critical don't on this list. Controlling moisture to keep it out of the building prevents damage to many parts of the building, as well as keeping the homeowners healthy. Wet buildings grow mold.
4. design a leaky house. Simple and proper air sealing details can make a home go from a sieve to an airtight chamber, and can reduce the heating or cooling load in a home by as much as 20-30%
5. design a thermal bridge. Many techniques, like advanced framing, and continuous insulation on the exterior of a building, can prevent a lot heat loss through building components.
6. leave out a ventilated rain screen behind the cladding. This gap promotes thermal performance of the wall assembly, and avoids trapping moisture.
7. choose products before process. Select the products to achieve the specified building performance and construction techniques, not the other way around. Selecting products first could drive up costs and compromise the homes overall performance.
8. forget to design for slab edge insulation. Depending on the size of the home, and where it is located, as little as ½" of slab edge insulation can reduce its heating load by 20% or more.
9. let the HVAC contractor over-size the heating and air conditioning systems. A correct Manual J load calculation can show that a home needs half or less than a typical "rule-of-thumb" method of sizing.
10. forget the Ventilation (the "V" in HVAC) that provides fresh air to the home. People need to breathe.
11. put mechanical equipment in unconditioned space. This makes the equipment work harder and less efficiently, increases the heating and cooling load, and wastes energy.
12. ignore ductwork. Designing the architecture, structure and mechanicals to integrate with one another is simple when you do it all at the same time.
13. design one component of the house at a time. The house is a system. Well, actually it's a home for people to live in, but it's also a system much like an eco system. The building and all of the components inside and out make up a network of many smaller systems that must work together as a whole; as an integrated system. Everything affects everything.
14. and finally, don't, under any circumstance, design an ugly home. "It's not sustainable"*. Plus, it's ugly.
*Quoted from Joe Lstiburek, PhD, P. Eng, ASRAE Fellow – Building Science Corporation. Some call him the "Father of Building Science" in North America.
This is just the beginning.
I will be re-visiting this soon to add more Don'ts to a long (forever) list. In the meantime, let's hear from you, the reader and observer of other failures or mistakes, about the kinds of things you see that we shouldn't see in our homes. It may just show up on the next list, and it may just save a home or building!
I'd like to see the roll of building scientist shift to architects. We have the greatest amount of control and responsibility on how a building is to look and perform, and mostly the profession shirks this responsibility and leave it to a builder, or as Dr. Lstuiburek puts it, to "by others". Our home and building owners' health, safety and welfare are in our hands, let's not let them down. As architects and designers, we took an oath!
Thanks for visiting the blog. Enjoy the rest of your day!
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