11 Building Science Secrets Every Home Builder & Remodeler Should Know
Overall, the state of the construction industry is improving. A lot of home builders and remodelers are learning, either out of interest or coercion, about building science and how to apply it to their work.
That's a good trend, but an 'overall' statement like that is mainly a feel-good thing. Yes, we're headed in the right direction. Remember that old joke, though, about the man who drowned in a lake that had an average depth of only two feet? Plenty of builders and remodelers aren't getting the message, and plenty of houses are being built with problems that shouldn't be that hard or expensive to fix. Some of the fixes even save money!
Here, then, is a start. The 11 'secrets' below aren't really secrets (well, number 11 sort of is), but judging by some of the conversations I have with people in the construction industry, they might as well be.
- House wrap isn't installed to be an air barrier. It's almost never sealed well enough for that, and it doesn't work in both directions. The real purpose of house wrap is to be the drainage plane behind the cladding. Related: House wrap isn't a vapor barrier either. Most are not even a vapor retarder.
- Power attic ventilators are a liability, not a feature. If you're still installing in them in homes, it's time to stop. There's a good reason they're banned by the Georgia energy code.
- A house does NOT need to breathe. People need to breathe. The house needs to have good control layers, including a continuous air barrier. Stop the random leaks and add an intentional leak called a mechanical ventilation system.
- A small uninsulated area can make a huge difference in heat gain/loss. Uninsulated can lights, attic scuttle holes, and other bare spots can lead to efficiency and comfort complaints from your clients. This applies as well to insulation that's not uniformly distributed.
- It's the processes more than the products that determine the quality of the house. Just because you spend a lot of money to install spray foam insulation, heat pump water heaters, and ground-source heat pumps doesn't mean that you're building a great house.
- When you attach high-efficiency HVAC equipment to crappy ducts, you're the equivalent of a snake oil seller. The buyers think they're getting something that the system can't deliver.
- Attic kneewalls need more insulation and an attic-side air barrier. Those walls around bonus rooms that separate conditioned space from unconditioned attic are a frequent cause of comfort complaints.
- Ducts systems should NOT be in unconditioned attics, especially in hot climates. There's plenty of help to do this right in new construction. In existing homes, you may have to do the best you can with you've got.
- Heat pumps can be more comfortable and efficient than furnaces in high performance homes, even in colder climates. Furnaces are often oversized. In cold climates, a hydronic coil supplied by a natural gas water heater can supply all the supplemental heat necessary.
- Ventless gas fireplaces are a liability. Yeah, the gas industry lobby is powerful enough to have kept them legal this long, but these things can be dangerous.
- In 20 years, every home will come with a Turbo Thermo-Encabulator Max. Or not. ;~)
That list should give you enough to chew on for a while. A good trend is one thing, but let's get this knowledge out there to turn the trend into a movement.
Flat or Lumpy - How Would You Like Your Insulation?
It's Not Just the Box - High Efficiency HVAC Includes the Ducts
How to Sheathe an Attic Kneewall — And How Not to