Let's see where I left off...
Wow. I guess a lot has happened!
All the plumbing and electrical "rough-in" got completed. Here's some interior shots of the framed walls:
The timber frame portion and ceiling of the front porch got installed! Still needs the metal roof, and the actual porch/deck part will wait (I think) until some dirt gets moved around.
Todd installed the ERV system, which stands for energy (or enthalpy) recovery ventilator. Basically it's a fancy ventilating system that always brings in fresh air and exhausts the stale air but captures the heat (or cold - depending on what you're trying to do) at a high efficiency to use with the fresh air. In other words, it moves the air (always fresh) throughout our space; and it manages the humidity. and it seems like a slick way to move air around without a typical furnace, dusty air ducts, uncomfortable air movement. It runs at a really low rate of air flow all the time, and consists of small plastic ducts that run through the stud walls and shouldn't collect dust and pollutants the way typical metal ducts do. We shall find out how it all works once we're living in it for awhile!
It's pretty much a necessity for a tightly sealed house, from the research I've done. Which brings me to...
The blower door test! This is one of those things that I and our builder kind of geeked out on. So hopefully I don't bore you with the following...! Feel free to tune out and skip to the end!
It's a way to measure how air-tight your house is and if done before drywall is complete, it provides a way to find leaks that can be sealed before the construction is done. In fact, it's such a key piece of energy efficient construction that air-tightness is a major requirement of certification under the "Passive House" standards that are modeled after Germam energy efficient construction methodologies. Though I did a lot of research and am quite familiar with several different energy efficiency models, such as LEED, passive solar design, Energy Star Homes, and Passive House, we chose not to follow one particular subscribed path in order to receive any official certification. Rather I used a variety of design principles and bits and pieces of each, as well as the help of an energy consultant out of Denver. The Passive House standard requires a strict air tightness measurement of 0.6 ACH @ 50 pascals (air changes per hour at a particular pressure). The Energy Star program requires between 3 and 6 ACH, depending on climate zone. I decided that I would be quite happy with a target of 1 ACH, so the energy model and the HVAC system were designed to that goal.
Why is air tightness so important, you ask? What about moisture build up, fresh air, letting the home breathe, etc? The way I see it (after living in several very leaky homes and wasting a lot of electricity to send heat right out the cracks around a poorly installed and sealed window, or right through poorly insulated floors and walls), I'd much rather have control over the ventilation and heating/cooling of the space rather than letting the leaks decide! Hence the ERV system discussed above.
Though it seems so important to me, our builder could only find one guy locally that has the equipment and know-how to do blower door tests. He's on the verge of retirement, but Todd hired him to come do the test and share some of the knowledge so that Todd (and maybe me some day....future career in energy consulting?) can take over being able to provide such a service.
Here's some pictures of the process. Preparing the blower door frame:
Getting the fan into place:
He prepped the system, turned it on and we watched eagerly to see where the numbers came in. The gauge measures cfm's of air flow, which then gets plugged into a formula using the volume of the house to get an ACH number, so we couldn't tell at first where we were at in relation to our goal. The tester was baffled by the readings on the gauge because it didn't at first seem to be reading properly. He even opened a window to see how it would affect the readings, and the numbers jumped accordingly. Then he shut the window again, and basically said the readings were so low, he wasn't sure it would even calculate properly. Sure enough, when he plugged it into the computer, the program said the cfm figures (~60 cfm @ 50 pa) were too low to calculate ACH. He tried a few different numbers that were artificially high, and it accepted ~75 cfm, which translated to 0.15 ACH, meaning we were nearly at 1/10th of our goal! Wow!
In his 30 years of doing blower door tests, he had NEVER seen a house come in that low, by a lot! Todd also testified that we had blown away (no pun intended!) the air tightness records that he had encountered among his SIP (structural insulated panel) colleagues!
Todd and I were pretty happy about the results for sure, but to rain on our own parade a little bit, it was so low that we both actually questioned the accuracy of the test. Was it done right? Did we miss something? Todd had definitely gone to great effort to ensure all leaks were sealed and that the high quality windows and doors I selected were installed properly. BUT, he didn't think he had done anything really out of the ordinary, and it is considered difficult to construct a house under 1 ACH. Also, to be clear, air tightness and blower door tests are by far not the only measure or indication of energy effiency or good quality, etc. (If you're still interested in all this and not yet bored by it, see the following for an in-depth discussion about this particular topic: http://www.buildingscience.com/documents/insights/bsi-053-just-right-and-airtight). There are plenty of people that don't believe that tighter is necessarily better; and/or that too tight can be problematic. Hence the "build it tight AND ventilate right" jist of the linked article. We're hoping that we got both pieces of that puzzle right!
And, because of our doubts with the test, we are actually having it redone next with a smaller fan that will hopefully give us a more accurate reading to at least have an accurate number to brag about!
Enough for now. Thanks for sticking with me. More fun visuals next post (hint: we've got drywall in place - it's really starting to look like a house)!
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