Winter in a Passive House
Andrea — December 30, 2012
We've been living in the house for a little more than four months now, but it seems like much longer than that (in a good way). The long ordeal of planning and construction has faded from our memories, and we're simply enjoying living here.
In most respects the house is performing extremely well. The 12,000 BTU heat pump is having no trouble keeping the entire house comfortable. Outdoor temperatures haven't fallen much below 20°F yet (-7°C), so it hasn't really been challenged, but we're not too worried. We left town for a few days last week and turned the heat pump down to 60° (it's normally set to 68), and it never even ran while we were away. The indoor temps ranged from 62-66°, even though outdoor temps stayed below freezing.
Our one complaint this winter is that the house has been extremely dry (relative humidity ranging between 20-25%), with our heat recovery ventilator running on low, at 62 CFM. This isn't too surprising, since Ted and I are only two people living in a fairly voluminous house without pets. We don't have any houseplants yet either, but I plan to remedy this soon by setting up our indoor vegetable garden upstairs (that will be a whole other post, hopefully in the near future).
For now our solution is to run a humidifier. (I know, so pedestrian!) The main problem is that the humidifier is quite loud, drowning out our whisper-quiet heat pump and HRV. Our long-term fix will be to add plants and see how that affects things, and then maybe get an ERV core for the ventilation system. It's pretty easy to swap cores, apparently, and the ERV will transfer moisture from the outgoing stale air to the incoming fresh air. Naturally, our many geeky onlookers (including Peter Schneider of Efficiency Vermont, who installed all the monitoring equipment) will be curious to see what difference the ERV makes for comfort and energy use.
You may have noticed that this post is called "Winter in a Passive House," and not "Winter in an Almost Passive House." This is because we built a full-fledged, certifiable passive house (pending the actual certification, which we haven't gotten around to yet). We made the decision ages ago, but I never changed the name of the site because I didn't want to jinx things. I'm not so worried now, since we did insanely well on our blower door test (91CFM, which translates to 0.29ACH50). I therefore feel pretty confident about our final PHPP numbers, even if we messed up a thermal bridge calculation or two.
I haven't decided what we should rename the site, so for now I'll just strike out the "Almost" and see where the spirit moves me.
Speaking of winter, here are some lovely new snowy pix!
Random Bits
Basement rim joist areas; holes cut for plumbing traps under tubs and showers; cracks between finish flooring and baseboards; utility chases that hide pipes or ducts; plumbing vent pipe penetrations; kitchen soffits above wall cabinets; fireplace surrounds; recessed can light penetrations; poorly weatherstripped attic access hatches; and cracks between partition top plates and drywall.
Re: Winter in a Passive House
Marilynn — January 10, 2013Hi Andrea and Ted
How has the winter been so far in your passive house? I am curious about a couple of subjects that I didn't read much about on your blog. What type of secondary heat source did you incorporate into your house. Has the sun provided enough/or too much heat? As well, water heating...how has the solar thermal system performed? Is there a need for back-up water heating? And, last but not least, how did you resolve your dryer conundrum?
We are in the final stages of design of our passive house and hope to start building as soon as the snow in the foundation hole subsides. The questions I have asked of you are still yet to be resolved for us. Any experience you can pass on would be greatly appreciated.
I always look forward to your latest blog posts.
Re: Winter in a Passive House
Andrea — January 12, 2013Hi Marilynn,
Our secondary heat source is a Mitsubishi HyperHeat mini-split heat pump. We got the 12,000 BTU version, as opposed to the larger 18,000 BTU model, and it's working fine so far. The temps dipped to -10°F a few weeks ago and it had no trouble keeping up.
The solar hot water system works with an electric storage tank, which provides backup hot water. On a cloudy day we don't get much solar water heating, but on sunny days it works great.
For now we've resolved the dryer conundrum by not using a dryer. Our old dryer is in the garage but we haven't bothered hooking it up—we just hang laundry to dry inside. I posted an update (with photo) just now.
Re: Winter in a Passive House
Marilynn — January 16, 2013Thanks for your reply, Andrea. This is the interesting stuff about passive houses. There's plenty of "building" info to be found on the web but not a lot of (comprehendible) "living in a passive house" information. An excellent example of this is Ted's comment in the following post about not getting condensation on the windows because of the HRV...good to know! Thanks for sharing. I look forward to more of your experiences of living in your passive house.
Re: Winter in a Passive House
peter shaffer — January 7, 2013Hi there,
I love your website. We're in the process of moving to VT this summer and then onto building a passive house. Your house is beautiful and I love the sun coming into your house. I live in Portland, OR and we don't see the sun much. What the price per sq ft (including foundation, PV, appliances, heating/cooling, etc..) for the whole house?Your website is great for us beginners. Thanks.
Re: Winter in a Passive House
Andrea — January 8, 2013Congratulations on moving to Vermont—we love it here.
I don't have exact calculations on our price per square foot yet, but unfortunately it is painfully high (above $200/sf). But other people manage to do this for a reasonable cost, so if you plan carefully you can probably spend a lot less than we did.
One of the things that really added cost was the height of our house—everything had to be done from scaffolding. If you don't care about having a dramatic roofline, don't have one. I don't think I'd change ours, but our shed roof added a lot of cost. It also required the construction of an awning to hold the solar panels, and Eli pulled out all the timber-framing stops on that one.
Another thing that added a ton of cost was siting—if we had it to do over again we might have chosen a different site; the one that we chose has a lot of ledge and an inconvenient slope, plus it wasn't terribly amenable to south-facing windows. That's part of why the house is so high and the foundation so complicated.
Also, a lot of our costs came from having built an entirely custom home. We didn't set out to make everything incredibly complicated, but it seemed to turn out that way.
I'll eventually swallow what's left of my pride and do a blog post about why our house cost so much, and how other people can hopefully avoid our mistakes, or at least make them with open eyes.
Re: Winter in a Passive House
Eric — January 12, 2013Custom costs are high - it's much cheaper to have a crew knocking up several houses of the same type over a few weeks.
Many under-estimate the cost and that was a major factor with out co-housing group blowing up - expecting well designed and built homes for the price $120/sq-ft.
One though running thru our mind (we're on the north half of a semi-detached) is that getting a regular 'burb home isn't so bad - as long as it has southern exposure. Our 20 year old home is $300/winter in heating for gas (plus almost as much in yearly connection fees) and going full passiv haus will not save that much. But we'd love the southern exposure to feel the warmth in winter and start garden plants - to have a cold cellar for storage. We're a family of 4 in around 1500 sq-ft and consider it too big. EcoVillage Ithaca friends say that 1200 sq-ft was fine for a family of four.
I've seen "green" homes that are a disaster - the subcontractors had no clue how to "do" energy efficiency, or even handle the materials, and really screwed things up.
We have one century home in town where the local energy-efficiency company went hog wild and cut the energy use to 1/10 of what it was (sub $100/winter in heating) - by gutting the inside and spraying in foam to air seal and add high insulation; while keeping the century old look of the home. But gutting the inside comes at a cost >$100k. Still - after a century a home deserves a bit of renovation.
Re: Winter in a Passive House
Andrea — January 12, 2013Ted and I are certainly in a large house for two people (2,000 sf), but in the past we've had long-term guests who stayed for months or years at a time, and we wanted a house that would happily accommodate that. And I must admit, we're enjoying having all this space. It's very compact—not sprawling—and it's nice having dedicated spaces for different parts of our life (work, meditation/yoga, etc.). A little excessive, perhaps, but our energy bills are negligible so far. Also, we wanted to build something that would suit a larger family, since we hope this house will outlast us by many years.
Too true about inept subcontractors... we prevented this by being complete and utter control freaks and also being wary of the lowest bidder. We initially went with a low-ball drywaller, for example, and he would have done a fine job if we were building a normal house, but we had so many pesky details that he quickly became difficult to work with. He had bid the job with little margin, and instead of raising the price on us he simply became a pain in the ass (for lack of a better description), griping about every little thing. We finally read between the lines and offered him some extra money, which mollified him, for the rest of the drywalling we decided to hire some guys we trusted on a time and materials basis. More expensive, but far less exasperating.
Re: Winter in a Passive House
Bob Swinburne — January 23, 2013While I am all pro-small house etc. I think sometimes that people build too small and create a house that will not serve a variety of occupants over the several hundred year (hopefully) life span. I caution people to ignore square feet and design something that will work for many possible situations. Which is not to say that it can't still be compact. Also having a big mudroom and pantry can add lots of square footage but add hugely to functionality. Which seems more sustainable to me. If you are doing the shell right (passive house) then the energy is all in the up front materials not in long term energy use.
Re: Winter in a Passive House
Andrea — January 23, 2013Alas, we don't have a pantry, but the utility room could certainly be adapted in a pinch. Currently the shelves there are loaded with paint cans (I know, bad for indoor air quality), etc., but those will migrate into the garage once we finish the trim and decoration stage. If my gardening exploits are successful (both indoors and out), I hope to eventually line those shelves with canned veggies galore.
Bob, I see that you live in Brattleboro — you should definitely come visit sometime soon! Send us a message through the contact form if you're interested.
Re: Winter in a Passive House
Bob Swinburne — January 23, 2013I'm an architect in Brattleboro - at the Cotton Mill - I also just finished the Passive House training and awaiting results from the exam. I worked for a bit with Eli way back when I was a carpenter for Mindel and Morse Builders.
Bluetime Collaborative
Robert Swinburne Architect, LLC
AIA, NCARB, LEED AP
72 Cotton Mill Hill
Brattleboro, VT 05301
(802) 451-9764 cell
www.swinburnearchitect.com
http://swinburnearchitect.com/wordpress/