Steps to Build Your Own House
My friends up in Maine came up with the concept of the Pretty Good House a few years ago, and I love the idea! Not everyone can or wants to build a LEED Platinum, Living Building Challenge, Passive House. But a lot of architects, builders, and homebuyers would like to design, build, and live in houses that are better than the barely-legal, code-minimum houses that populate the market. The Pretty Good House, then, is the way to go.
The 10 essential steps
If you're interested in designing, building, or living in a Pretty Good House, here are what I consider 10 essential steps you need to take to make it happen. It starts with applying the principles of building science. This is all stuff I've been writing about here for the past five years. Just put it all together, and you've got yourself a Pretty Good House.
1. Spend more time on planning. This was my biggest mistake in the house I built. I got rushed and ended up spending more time building the house and it cost more money as a result. Take all the time you need to get the details right before you move any dirt or lift a hammer. It'll pay off in the end. This is especially true for getting the HVAC done right. Most designs don't leave enough room for proper distribution of heating, cooling, and ventilation. Integrated design is where it's at!
2. Hire a third-party building science consultant. And get them involved from the very beginning. Choose one with knowledge and experience, someone who knows how to work with contractors and can stand up to them when necessary. A lot of good intentions and good designs get undermined by the crusty contractor who says, "We've been doing it this way for 30 years and we're not going to change now."
3. Don't cut corners on controlling water. Design and detail every aspect of the water control layers in your building enclosure. What materials are you going to use? Do you need a vented rainscreen? Do all assemblies have the ability to dry properly and not trap water? Most building failures are due to water.
4. Make sure the building enclosure is airtight. That means you'll need a blower door test. If testing for airtightness is new to you, do preliminary testing at the predrywall stage if possible. How tight is tight enough? Certainly no more than 3 air changes per hour at 50 Pascals (ACH50), but Passive House builders are blowing past the 0.6 ACH50 level required by that program.
5. Get the most out of your insulation. One of my earliest articles (Flat or Lumpy - How Would You Like Your Insulation?) was about how badly your insulation can perform just by how it's distributed. An extension of the same principle is that even a small weakness in your building enclosure's insulation can have a mind-blowing effect on performance. In short, a uniform layer with a lower R-value beats really thick insulation interspersed with little to no insulation. It's the thermal bridging, stupid! (If you want to go deeper, learn about the layers and pathways of heat flow.)
6. Pay extra attention to rough openings. Certainly this is true for controlling the flow of heat because windows have a lower R-value than the surrounding walls. Even more important, though, is that water leaks usually happen at the openings, so get those flashing details right! And of course, it's easy to make a significant reduction in your air leakage by sealing the rough openings...or missing your target because you didn't.
7. Hire the right company to design your HVAC system. That company might be the same company that installs your HVAC system. There are a few out there that are competent at this. What happens way more often than it should, though, is that when the installer also designs, you end up with duct disasters like this. What you really want is something like the one shown below.
8. Get the HVAC distribution systems inside the building enclosure. Forced air heating and cooling dominates the type of distribution in most homes in North America. Even with a perfectly designed and installed duct system, putting those ducts in an unconditioned attic can add 15% to your air conditioning bill. From a performance perspective, HVAC distribution needs to be inside the building enclosure. You can do it with ductless mini-splits, plenum trusses, and other techniques. Just do it.