utility bills I often hear the statement about no utility bills in a net zero grid tied home. I have a grid tied PV system, and my utility still charges me $10.89 /mo when I'm producing excess electricity. Is my utility somehow unusual? I suspect not but I'm curious to hear from others. This is an interesting project in terms of it's extremely simple approach and low cost, but from the limited photos the result appears pretty bleak (IMHO).
Posted: 11:40 am on October 16th 2014
Dana's comment Dana - You seem to suggest that randy's unvented roof would meet code with the correct vapor retarder, but the exception you note is for a vented roof (it just reduces the amount of ventilation area). Am i missing something in the code?
Posted: 07:12 pm on January 13th 2013
another example In case anyone is interested, a couple of months ago I posted on my blog similar information about a years worth of energy consumption for my own passivhaus completed in 2013. Granted it's located in a much more moderate climate, but for comparison our 1965sf (gross area) house cost about $375k to build including permitting, sitework, some landscaping, and a small PV array. http://www.insituarchitecture.net/blog/2013/08/08/is-it-working
Posted: 01:12 pm on October 20th 2013
I have a European lift / slide (Zola) door at my own passive house and you will find them in countless passive house projects. While perhaps not quite as airtight as a tilt / slide or swing door, they are still exceptionally airtight. I had the same concerns when deciding on a big door, but we had no problem achieving a .32ach50 blower door result. They are beautiful to operate, allow for really large openings, and you will not be disappointed.
Posted: 05:23 pm on October 26th 2013
I have to say this is a bit painful to read. I know there is a DIY aspect to this site and I'm sure I will get criticized for saying so, but you really should consider hiring a (good) architect.
Posted: 02:31 pm on March 22nd 2016
Conclusions I really appreciate the data shared in this post. It seems that one of the conclusions drawn is that actual performance doesn’t match the modeled performance for these two PH projects. It’s curious to conclude therefore that actual performance for the Code versions would match the modeled performance based on Katrin’s comment that the modeling is fairly accurate. While anecdotal, I consistently see multi-family projects all over my city with significant thermal bridging, no attention to air-sealing, poorly installed insulation, and never a blower door test. Code requirements are often (usually) quite different from the reality of construction. The claims of 90% savings for PH thrown around for years have always made me cringe. We need more data and less hyperbole. Still I would caution folks from drawing a conclusion from this tiny sample pool, and from applying this data to the performance of a single family residence. I published an analysis two years ago on my blog comparing the modeled performance to the actual performance of my own Passive House (http://insituarchitecture.net/blog/2013/08/08/is-it-working). It’s just one house and I intend to do a more current analysis, but one year’s data for my own house demonstrated that it exceeded the modeled performance. As an Architect and CPHC, I consider myself an advocate for high performance building and the energy modeling is just another tool. Most of my recent projects, while modeled in PHPP, have stepped away from meeting some or all of the PH criteria. I look forward to evaluating the actual performance of these projects in addition to the perceived comfort; like everyone I’m seeking that sweet spot.
Posted: 03:42 pm on August 23rd 2017
Mountain, I agree that the exterior layer of mineral wool is a better choice than foam for many reasons. I have used mineral wool on a number of projects (both residential and commercial) with builders that have never used it, and particularly at 1 1/2" it really isn't that difficult to install properly. It is usually held in place "temporarily" with a few cap fasteners and then the furring strips are fastened through it to do the work. I would suggest sealing the seams of the plywood using a good quality air sealing tape (like Siga Wigluv) if you are working in dry weather or Prosoco Airdam if it's damp to create the air barrier, and then using an inexpensive permeable WRB on top prior to installing the mineral wool.
Posted: 02:34 pm on April 17th 2018
I agree with both Dana and Jon. More exterior rockwool would be better / safer as would adding Membrain at the interior if you can. I'd stick with the plywood as exterior air barrier and would ditch the spray foam. All this talk about walls (the easy part) but what about floor and roof and the transitions?
Posted: 10:02 pm on April 17th 2018
Good summary of the pros and cons of each approach. In my limited experience trying to get a centralized system in a multi-family project, the need for fire / smoke dampers at each fire barrier penetration added significant costs and perhaps should be added to the discussion.
Posted: 01:01 pm on October 9th 2018
oops - I see it is in the list of cons already. my mistake.
Posted: 01:02 pm on October 9th 2018