Things are going swimmingly. They poured the piers yesterday, and the dismal unending rain means that the concrete will probably cure to maximum strength. We've also hammered out all sorts of details with Eli, Marc, and Ben, and a lot of problems and challenges seem to be melting away. I figured out a more attractive and efficient way to add solar electric and hot water (new drawings forthcoming), and everything is looking great.
The problem? Our many envelope tweaks and revisions have brought us tantalizingly close to Passivhaus performance levels. This is bad simply because we now have to decide whether to bite the bullet and pay the extra $3,000 (or more) to make it happen.
The return on investment will be lousy. The difference in utility costs between the house we're building and a certified Passivhaus will probably be less than $40/year. We've already ordered Passivhaus-certified windows and are seriously considering paying extra for a Passivhaus-certified HRV because of its many good features. And of course we've minimized thermal bridging in the envelope and are wrapping the house in heaps and heaps of dense-pack cellulose, plus a 4" exoskeleton of polyisocyanurate.
But we haven't paid the $1,500 (give or take) to have Marc model the house in PHPP, the über-spreadsheet that analyzes every detail of a house's energy performance. And you can't have a certified Passivhaus without running it through PHPP.
Of course, PHPP is only the first step. Odds are that we'll fall a little shy of the Passivhaus performance requirements, so our next move will be to add more insulation somewhere or tighten up the envelope a bit better. And that will cost more money than it will ever save us.
So why bother? I don't think I'm attached to having a certified Passivhaus. As you can see from the name of the website, I'm quite satisfied with our not-quite-passiv status. Also, I seriously doubt it will make a difference on resale whether the house is certified or not, since it's going to be a freaky-efficient house either way.
But there's a symbolic value to getting certified. Only a handful of certified Passive Houses have been built in the United States, which means it's still an inspiring new concept. One of our major goals in building an energy-efficient house is to inspire other builders and homeowners, and having the Passivhaus label and certificate will help get the word out.
Several people working on the house, both directly and peripherally, have told me how exciting it is to work on such an efficient design. They really like seeing someone do it right and not cut corners on energy performance. We're trying to practice "trickle-down green building," meaning that the way we're building this house will hopefully catch on and eventually become the new normal, at least to some degree. Building an actual Passive House rather than an Almost Passive House might further this goal.
Does that count, or should we just return to the ROI and call it a day? I should add that building an affordable house is another one of our goals, because it's not very inspiring if only people with endlessly deep pockets can build this way.
Ordinary houses breathe through leaky joints and poor seals, losing heat and wasting energy. But our house won't leak, so we'll use a heat recovery ventilator (HRV) to admit fresh air and expel stale air, transferring heat from one stream to the other.