Blower Door Test

dekeoboeMay 2, 2012

Today we conducted the post-construction blower door test. We got a .57 ACH at 50Pa for pressurization and a wonderful .28 ACH at 50Pa for depressurization. Because there was a significant difference in the two measurements, we moved to another door (we thought there might be leakage around the blower door at the strike-plate) and did some additional sealing of the ERV and make-up air ducts. In the end, the results were nearly identical with a .56 for pressurization and .28 for depressurization. Averaging the two out that provides an overall .42 ACH. We are aiming for Passive House certification, so we are happy with the results.

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phoggie

Well, you lost me.....I have never heard of a blower door test....so will you tell me about it? Thanks!

    Bookmark   May 2, 2012 at 7:18PM
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david_cary

Blower door test checks the amount of air leakage on the house. Since infiltration is a significant source of heat loss and gain, the infiltration number is important for building an efficient house.

Many areas are starting to require these on all new construction - like Georgia for example. Who would have thought Georgia?

FWIW - infiltration is significantly more important for heating. My audit had baseline infiltration only at 2% of cooling load but 20% of heating load. Which really makes me surprised that Georgia requires it. It is simple to cut this number in half. Going to Passive House standards is a more difficult proposition.

    Bookmark   May 2, 2012 at 8:41PM
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sajakh

David,

What is a typical breakdown for the cooling load in a Georgia home if baseline infiltration is only 2%? I am interested to know how much does windows and their SHGC factor in the cooling? Also how much does interior window shades make a difference in the cooling load? Thanks

    Bookmark   May 3, 2012 at 9:15PM
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lzerarc

dek-can you post more information about your house? I sort of recall seeing posts from you in the past about your home, but do not recall seeing anything that stood out at me at anything near PH levels. (as far as additional items besides air tightness, such as power consumption, insulation levels, window tightness, etc).
Obviously those items I listed are not a direct requirement of PH certification, but they do directly affect the results of achieving it. I am interested in seeing your project and the products and methods you have used.
btw- good blower door numbers! congrats.

    Bookmark   May 3, 2012 at 10:05PM
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david_cary

Solar gain 40%; Internal gains 30%; Walls/ceilings 20%; Ducts 10%. Ok that is some guesstimate based on my energy audit which did have a decent amount of E and W windows (making the solar relatively high - they were typical low-E and I have no idea what SHGC that would be).

Obviously ductwork entirely in conditioned space erases that 10%. So doing a better job on windows and putting ductwork in conditioned space could make that 2% closer to 5%. But that also was "typical new construction" when cutting that by 80% is pretty easy and you are back to 1%.

I suspect internal gains is a lot lower with LED and CFL lights. So again you can raise the relative amount of infiltration even more.

    Bookmark   May 3, 2012 at 10:46PM
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dekeoboe

lzerarc - Probably more information than you want to know can be found at my husband's blog. He is better at the technical stuff though, so hopefully you can find what you are interested in there.

Here is a link that might be useful: our house

    Bookmark   May 3, 2012 at 11:25PM
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lzerarc

deke- thanks for the link, I have actually saw it before from your DH. small world, I was just talking with him on another forum about your tilt and turn windows! I stand corrected, I have not seen your home posted on this forum that I can recall...can not believe I missed it. Wonderful project. Great blog.

    Bookmark   May 4, 2012 at 12:05AM
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david_cary

Nice blog. I am very impressed on the amount of resources you put into saving energy. I'm just wondering if there was ever a discussion that you were going a little overboard.

In our climate, a well oriented and sited house with good air sealing and r-40 walls would use so little HVAC, that geothermal is overkill. At some point there not only is zero monetary advantage, there is also zero environmental advantage. The amount of energy inputs into construction may take several centuries to be recouped.

But I get it. Don't forget your transportation - you have to have a spot for solar panels to charge the EV and I didn't see that.

    Bookmark   May 4, 2012 at 5:33AM
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lzerarc

d_c is right with many of the PH stuff, IMO, tend to not pencil out. Some PH certified tilt turn windows from Germany, for example, can cost 2-3x that of a good window from here (Marvin). While the performance of these are much better then a Marvin (or about any US big company) they still seem to rarely pay off. However they are typically needed to get the loads low enough to hit the PH requirements. With that being said, high performance windows have other advantages such as physical comfort when sitting beside them on a cold day or night. You can also typically have single source ducting that does not have to be placed at an exterior wall as there is no need to wash the windows with air.
However some upgrades do not need to always pencil out...there are ones that are peerly "wants" or "feel good" upgrades. Interesting enough, bascailly all interior cosmetic upgrades fall into this category with 0 pay back, and people do not blink an eye at dropping another 5-10k over budget on counter and cabinet upgrades, yet anything shell upgrade wise seems to NEED a payback associated with it to even consider it. Payback may or may not be there, but they typically come with increased comfort within the home. That needs to have a value placed on it as well.
Geo in a high performance house, such as a PH is typically not worth it, unless it is a larger home. This house appears to be larger where a 2 ton unit can probably be appropriate. Depending on incentives from the feds, state, and local power companies, geo units can cost the same....or in my case, less....then a standard 95% furnace.
My soon to start 15/28/42/65 r values shell is using geo. After rebates from feds and the power company, the 2 ton unit costs roughly the same as using 2 Mitsubishi hyper heat mini split units installed, which a lot of super insulated an PH homes use. You still need to add ducting for the HRV to that, which I was also including in my "about the same".
The added insulation and framing to achieve the values above is about $3000 to the entire project. Windows I have not decided on, but that could add a couple more k depending what I go with.

    Bookmark   May 4, 2012 at 9:12AM
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dekeoboe

Yes, our German windows were expensive. However, we wanted tilt turn windows and could not find a good quality US made tilt turn window. We looked at one of the Canadian brands and did not find the quality we wanted there either. I had a long list of companies that we looked into before deciding on the windows we went with and we are very happy with our choice.

Geo was not our first choice. We ended up going that way because of other things that occurred during the building process.

I agree with lzararc, wants vs needs and payback considerations are all individual. That's why we build custom homes.

lzararc - I am familiar with the thread on the other forum.

    Bookmark   May 4, 2012 at 10:59AM
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