14 Design Don’ts for High Performance Homes, Part One

12 donts 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.

Don’t…

  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!

SOAP BOX

I’d like to see the role 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!

image of Stop Sign, from PublicDomainPictures.Net

written by Chris Laumer-Giddens

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15 Responses so far.

  1. I have found that the proper use of ERV’s, Energy Recovery Ventilators, provide a great source for the “V” in HVAC that allows exhaust and fresh air, along with the recapturing of approximately 80% of conditioned air. When used in bathrooms in lieu of your typical exhaust fan, it serves as a great use of equipment for a healthy home with energy savings. This unit is seldom seen in residential construction and in my opinion, should be considered standard equipment within our homes systems.

  2. Jake Vierzen says:

    One that I would add is don’t separate the air barrier from the insulation layer. The two need to be in alignment, and ideally, contact with each other.
    You alluded to another with the vapor barrier comment, but don’t forget to plan for the assemblies to be able to dry, and toward both directions!

  3. Larry, you’re right on with the “proper” use of an ERV. There is no one size fits all approach to ERVs or HRVs. A lot depends on the unit that is specified, and the homeowner behavior, construction quality, the location and climate zone of the home, occupant health conditions, etc. one example that makes the point well is a homeowner suing the HVAC contractor because of serious mold issues in their home. The culprit was the ERV being connect to the bathrooms for recovery and exhaust. The homeowner took really long hot showers. The ERV re-introduces some of the “recovered” moisture in to the home as it passes through the core of the ERV, where the recovery enthalpy transfer (heat energy and moisture) happens. In this case connecting to the bathrooms is not recommended, and depending on location, even an HRV (heat transfer only) may not have been a good choice. Re-introducing moisture can be a good thing in certain homes, and that’s why ERVs are used more than HRVs.

    Every house and situation is different

  4. Spot on, Jake! Putting the insulation in contact with the air barrier helps prevent condensation in the cavity (floor, wall, roof). This is overlooked a lot in floors over unconditioned spaces, and most of the time there isn’t a true air barrier. Plus, the use of tigers teeth to hold the insulation in place compresses it and reduces the effectiveness of the insulation. This a bit off track from your comment, but also some common practices to avoid.

    The drying potential of walls can be a very difficult one to understand for most building professionals, because of how “it has always been done”. When I teach building science, this is one of the areas I need to spend more time on. It’s very easy to get this wrong.

    Thanks, Jake

  5. Ok I was with all of this right up to the point i saw the idea of putting the design into the hands of the architects. Educate the builders and architects together. Don’t leave us out in the cold. I have 37 years building the most energy efficient, healthy, and comfortable homes and dont need or want to be told by someone sitting in an office how to do it! You learn by studying yes but by doing is the best education. Continuing education that is available at the NAHB shows involve both the builders and the architects with book and hands on experience.
    Just sayin!!!

  6. John Kuiper says:

    I like Jake’s comment. I see too many cathedral ceilings and knee walls with open fiberglass on the back side.

  7. Dave Eakin says:

    I was with you until you hit #14. Ugly is allways in the eye of the beholder. I see lots of plans, designs, and finished houses that put lots of effort/$ into the “money side” (i.e., the side that most neighbors/passers-by see; the street side) that has no benefit to the inhabitants. In fact, most of these designs are detrimental to the inhabitants (not enough privacy, sun-fading of close in closets, little sun lighting into the interior, etc.) I would much rather live in a home that was “not ugly” in the views that I would see most – the interior (ref: Sarah Suzanka’s book series) with much less attention to those views that others see (and that I only see when first entering). Check those egos at the curb; better yet, chuck those egos.

  8. Prescott says:

    Good work Chris. This is an excellent list!

  9. Donald: I agree with you. I suggest that architects need to control the building science only as much as we control the aesthetics. When the house is finished, it looks the way it does because of the collaboration with the architect and builder during the construction process. The same should should be said for the performance. Neither the architect nor the builder should have complete control, and both should be working side-by-side for the best result.
    Thank you, Donald. Very good comment.

  10. Dave: I agree with you to the extent that we all have our own version of what is ugly. We must also consider, to the extent that we can, that there is a “collective” opinion of ugly, and that someone may eventually buy the “not-ugly-in-your-eyes-only” house, and may tear it down and build new because they like the lot but not the house. This is why we have design review boards, and one of the things that architects are responsible for. If we just design and build homes that are “not-ugly-to-me” only, we’re not sustaining the future.

  11. Thanks Prescott!
    It’s a list that could probably go on forever, but these seem to be pretty fundamental.

  12. Item #2 should be corrected. It is good practice to use Air Barriers not Vapor barriers in Walls. Also an Air Barrier is on the warm side and the insulation should be outboard of the insulation thus reducing any thermal short circuiting. Also a vapor barrier should always be used under the concrete slab on grade and under the roofing membrane or shingles.
    Dominic Vecchione

  13. Dominic,

    It is not just “good” practice, but best practice to put an air barrier throughout the entire building envelope (Walls, Floors and Roofs/Ceilings), not just the wall.

    I agree that the best place for insulation is on the outside of the wall, in which case the air barrier is best on the “warm side”, as you point out. If the insulation is inside the wall cavity, though, than the air barrier is better on the “cold side” to prevent any moisture from getting in to the cavity. If the wall is designed and built properly, it will allow any moisture that does get in to dry to the outside and to the inside.

    I’m not sure, but you may be confusing the point of this list. They are all things NOT to do. I am suggesting “Don’t” do these things, rather than “Do”. So, item #2 is saying “Don’t” put vapor barriers in walls, as you point out, unless your really know what you’re doing. It also says that under the slab and foundation is the only place where it there always should be a vapor barrier. I hope that clarifies it for you.

    As for “under the roofing membrane or shingles”, that would block the outward drying potential of the roof assembly, assuming the insulation is within the roof assembly. A weather resistive barrier (not a vapor barrier) is appropriate and recommended in this application. Either roofing felt over sheathing, or ZIP System Roof Sheathing that has an integrated WRB are recommended.

  14. Gary Miller says:

    Great list, Thanks

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