Blower door test scores
bAsqtBArKH
| Posted in Energy Efficiency and Durability on
I recently completed a prototype home that I am doing a blog on: affordablegreenhome.blogspot, and wanted to share my blower door test score: .48 ACH50. My questions is: Can others share their blower door test results and strategies they may have used to make the building envelope tighter?
Thanks,
Craig T. Payne
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Well, now that you've set the bar that high it's going to be hard to get other players. Nice blog, nice house, it looks like you went SIPS (?) & spray foam on your envelope, and used a relatively simple shape.
OK, I'll bite. I got 0.65 in January. Wall is double-framed, with dense-packed cellulose. Outside, the Typar is tape-sealed at all joints and tears, and a bead of acoustic sealant seals it to the bottom of the sheathing outside. I also foamed up under the bottom of the sheathing where it overhangs the foundation insulation. However, I established the primary air barrier inside, using MemBrain smart vapor retarder film. During framing, strips of poly were placed under all walls before being tilted up, and strips of poly were placed also atop all outside walls and on top of all interior partitions on the upper level. MemBrain on the ceilings under the attic were taped sealed to the strips of poly before sheetrocking that ceiling and insulating. After insulating the walls, the MemBrain was applied there and tape-sealed to the strips of poly at those perimeters. All pipe and wiring penetrations through the thermal envelope were foam-sealed. All this has been described by others in their efforts. I haven't done anything novel. I just paid attention to detail and did a lot of the picky detail myself. I also had a good crew who understood I was doing something different from what they had ever done before and gave complete cooperation.
I got a 0.479, with the chimney left unplugged (the dog ran off to hunt seals). It's a 296 sf igloo with salt-water dripped into the ice block seams. (Salt water is more flexible than fresh).
Sorry John, I got you beat...
0.476 ACH50 on a 283 sf mud hut (igloo shape) in the Pacific Northwest. Lots of clay, little straw (the air runs down the length of the straw). I had a sealed the 1-0 x 1-0 chimney... but had a 2-0 x 2-0 window open with no glazing since a neighbor thought my structure was ugly and threw a rock through the window (A triple glazed Optiwin and 60% SHG... Ouch. That hurt!)
Now I got plenty of thermal mass, but pretty poor air-sealing.
I have now turned off the HRV.
I tried both salt water and fresh water and found that while salt water is definitely more flexible, we have an abundance of fresh water. I came up with a 1000 : 1 mixture of fresh water to Morton's Table Salt and was able to get back some of the elasticity of Natural Salt Water that you indicated.
My SIGA Tape did not stick well to the wet mud, so on this one... No tape used.
CRAIG: In all seriousness: Nice job and good numbers. If you were a member of Passive House Northwest, those numbers would earn you a six pack of beer at every conference.
Yeah, I'm not the most techno savvy...I'd like to read the blog, how do i do that. what is the actual URL?
try this
http://www.affordablegreenhome.blogspot.com/
Craig,
Thanks for sharing.
I am not too surprised that only one person has accepted your challenge.
Perhaps your challenge has caused some "shrinkage" ;-)
http://www.youtube.com/watch?v=1cUNNKzj_Nc&feature=related
When I finished my home(near Dallas,TX) in August 2008 I was proud of my Results.
386 cfm at 50... 1.4 ACH50...HERS index 51
Simple House Shape.... 3 gables (2 ridge and 2 valley roof)..not over-glazed
Conventional stick built on slab with full OSB sheathing and Open Cell spray foam in the stud cavities and rafter encapsulation at the roof deck....careful attention to caulk&seal at wood to wood and wood to slab.
I WAS pretty proud until I became aware of Passivhaus standards in December 08.
After learning about PH I became GUNG HO about Super-Tightness.
Currently I am having second thoughts(thanks to Straube,Holladay & Riversong) about Super-Tightness(< 0.6 ACH50) and whether or not it is really worth the effort.
Craig, did you consider the difference in Energy savings between 1.5 ACH-50 and your 0.48 ACH-50?
I am going to guess that in your climate it is not a big value.
Or is your reasoning for Super-tightness related to Durability concerns?
John,
"Currently I am having second thoughts(thanks to Straube,Holladay & Riversong) about Super-Tightness(< 0.6 ACH50) and whether or not it is really worth the effort."
I'm surprised by this comment. Why is it that "Straube,Holladay & Riversong" have you second guessing < 0.60ACH??
Testing less than 0.6ACH is really not even an question anymore for the (now experienced) builders I work with, and or supply products to. These projects are using varied methods and having great success in both the time it takes and the results.
For yours and Craig's benefit, here are 5 of the projects I worked with, supplied, or watched in person or remotely:
Dan Whitmore's Seattle Passive House: Combination of panel adhesive and SIGA Air-Sealing. 041ACH.
Joe Giampietro's Mini B (Seattle): Liquid applied WRB: 0.40ACH50
Blake Bilyeu, Salem Oregon: Gaskets and 3M tape at exterior sheeting, 0.20 ACH50. An exceptional effort!
Artisan Group North Project: SIGA Tape, 0.38ACH with a large glazing missing and sealed with Tyvek!!
Artisan Group Freas Project: Gaskets, SIGA Tape, 0.48ACH and missing a door (sealed with Tyvek)
The list goes on. I'm consulting and supplying material for projects all over the US and Canada. Please don't mistake this as a pitch for product. It's not. I know all of the above builders personally. They are at the point that getting below 0.6ACH 50 is no longer a challenge. It's now just part of what they do...
If your going to ventilate, then your going to make a tight enclosure anyway. Once you design and reach around 1.5 ACH, it's not much more effort (or cost!) to get below 0.6ACH 50. It's all in your design approach and the detail follow through. It's the singe easiest... and least expensive energy efficiency measure at your disposal.
None of these projects had to resort to a spray foam- closed or open. As such, the air-sealing itself did not affect the vapor profile and did not overly complicate the design or build of the project.
Air-sealing is such an easy target these days!
John,
Btw... In my opinion, air-sealing is equally important in a heating, or a cooling climate!
Albert,
To be clear.... I agree about the importance of very good airtightness and I certainly agree that it is IMPORTANT in cooling climates and especially in HUMID climates.
My "second thoughts" are only about SUPER Airtightness(PH standards)
I am pretty sure I can dig up comments from Lstiburek, Straube, Holladay or Riversong that "question" the need for "0.6 or better" ....which person would you like me to quote or reference?
John,
Glad I misunderstood you.
"I am pretty sure I can dig up comments from Lstiburek, Straube, Holladay or Riversong that "question" the need for "0.6 or better" ....which person would you like me to quote or reference?"
Of your "Holy Trinity", I'd be curious of what you find in comments from Riversong and Lstibureck. Martin we can ask ourselves.
Martin and I "went a few rounds" over PH and subslab foam. I don't think his issue with this aspect of the PH standard transfers over to air-tightness. In the prior issue, it was a debate over the strategies of two different "programs": PH and US Net Zero builders. Both have VERY worthy and very BIG goals. They just employed differing approaches: Passive material investment (insulation) vs active mechanical investment (PV). Again... Both were reaching for incredibly high standards.
Once you start reaching 1.5ACH50, Air-sealing to the PH 0.6ACH 50 doesn't require the level of investment in material or labor that would make it a diminishing return. To reach a 1.5ACH level of air-tightness, it's takes the right details at the planning stage. Once there, it's not really much more to take it down to 0.6ACH 50. It's just good followthrough on the details.
Air sealing is a case where most of the material needed is on the site already. It's just employing it differently. The added material needed to seal by tape is really small. If the solution is to build the same house with no detail change and just add air-sealing by spraying foam, then to me, thats just adding a band aid to an existing defect. And... that band aid can negatively affect the building physics as well.
Martin, would you care to express your current opinion your self?
Albert,
About 2 years ago I asked Dr Joe his opinion of PH airtightness after this podcast...
see comment #2
https://www.greenbuildingadvisor.com/blogs/dept/building-science/perfect-wall-roof-and-slab-building-science-podcast#post_comments
As for Riversong...he was often critical of PH airtightness.
I think he even started a thread about it.
I think we should move away from sprayfoam.
I think Gaskets,Goo,Tape, Airtight Drywall and Airtight Sheathing are a better "direction".
Great Stuff John,
Thanks for looking it up.
I feel a little awkward in suggesting that our leaders in research and popular opinion should consider revisiting their opinions. A little like a student asking the teacher to smooth out his/her grading curve so that the whole class will have to work a little harder just to maintain a position in the middle .
Air-sealing with the wrong tools on a mediocre design is certainly an exercise in waste and frustration. Air-sealing with the right tools on a good design that takes it into account at the outset, is not a significant, or costly, obstacle anymore.
Dr Lstibureks comments are now two years old. I wonder if they have changed as he's seen skill and practices improve? His statement read to me as a personal opinion rather than the outcome of a cost/benefit study.
I've found air-sealing to be like running. If you're not in good condition, the first few runs are brutal. Once your condition improves, short runs are no longer challenging and your able to take on the longer trails.
"As for Riversong...he was often critical of PH airtightness."... There's not much I can say to that. PH is challenging to many... And many in the industry recoil from it seeking a less challenging path. All paths that significantly increase building efficiency are in my opinion GREAT and deserve support and respect.
This is just simple air-sealing of an envelop. 1.5ACH50 or 0.6ACH50... It's not that tough. Since I'm the principle of The Small Planet Workshop http://www.smallplanetworkshop.com, I spend a great deal of time on simple air-sealing products and practices with builders. The products complete with videos are at http://www.air-tightconstruction.com . On Monday I visit two more builders in order to help with air-sealing practices and material.
It not too tough if you start with simple tools, on a design that takes the air barrier into account at the beginning. Put the air barrier at either the inside, or on the outside sheeting. Either place is OK. For US single wall stick frame builders, placing it at the exterior sheeting is the easiest transition. The Passive House Builders who work with diffusion open wall systems with OSB or plywood on the interior are even easier to air-seal. The important part is to bring it consistently around the envelop, hopefully on the same layer with no breaks. The key is to keep it planned, visible and accessible.
When your projects are showing results at 3.0 ACH50, 1.5 sounds like a high bar. 0.60 ACH 50 is only a challenge until you get there.
If I have to choose sides in this debate, I guess I'll have to side with Albert.
1. Most cost-benefit analyses of air-tightening measures show a very positive return, even down to Passivhaus levels of air-tightness. I think it's money well spent. As usual with any such recommendations, though, there are caveats: the payback for extreme airtightness is faster in very cold climates than in moderate climates, and the return on your investment will only make sense if you choose an air-tightening protocol that is well thought out and doesn't take ridiculous amounts of time or materials to implement.
2. In the past, however, I have criticized Passivhaus adherents who state that a house that leaks more air than a Passivhaus is at risk of structural failure. Such statements are exaggerations.
Thanks Albert & Martin,
I actually prefer to obsess over airtightness.
Your comments have helped me with my "second thoughts"
I think that Affordable, Buildable Extreme Airtightness IS a worthy quest.
It would be interesting to hear if John Straube or Joe Lstiburek have revised their thoughts on the merits of Extreme Air Tightness?
Martin, you wrote "1. Most cost-benefit analyses of air-tightening measures show a very positive return, even down to Passivhaus levels of air-tightness. " Do you have any sources you can cite for this?
Wouldn't it completely depend on the cost to achieve the leakage reduction. Going from 1.5 ACH50 to 0.6 ACH50 might save about $15-$20/yr in heating costs if you have balanced (or no) ventilation and don't change the ventilation rate to account for the added leakage. If it costs $1000 to achieve this savings, is it worth the 50+ year payback? Maybe you should invest more in LED lighting or even an LED-backlit TV? It's not at all clear cut.
In addition, if you use continuous exhaust or supply ventilation, then there are no energy savings from the leakage reduction as the fan will control the air exchange rate completely.
Michael,
I was thinking of a cost-optimization study for net zero homes in Canada; the paper was written by Gary Proskiw and Anil Pahrek, and was summarized in the January 2011 issue of Solplan Review. In all four studied climates (Vancouver, Winnipeg, Toronto, and Yellowknife), the authors concluded that measures aimed at making the homes "as tight as possible" were cost-effective compared to PV.
I know you probably want more details -- indeed, I have my own questions about how the authors reached this conclusion -- but it's a citation. If I have more time later, I'll see what else I can dig up.
Martin,
"Passivhaus adherents who state that a house that leaks more air than a Passivhaus is at risk of structural failure."
That statement sounds down right bizarre... I can only hope that it's out of context or mistaken.
I can't imagine a situation where a difference of 0.40ACH (the net difference between 0.6ACH50 and 1.0ACH50) would spell disaster at 1.0ach and not at 060ach for a particular wall assembly in a particular location. If that was the point, then it's an "iffy" assembly at best.
My interest in air-sealing is strictly related to energy consumption. And... my bias, yes I realize that it's a bias, is that it doesn't end at cost justification per project as a measure. The benefits of EXCELLENT, while still REASONABLE air-sealing when looked at on a national basis extend to substantial environmental benefits beyond one individuals rate of return.
Michael,
I just re-read your post. $1000.00 to go from 1.5ach to 0.6ach? That must be a ball park right? My experience is taking projects all the way to 0.6ach50 for that or not much more in total.
This assumes good windows and doors to begin with... And perhaps an air-sealing "friendly" design.
Albert,
The "downright bizarre" assertion is Dr. Wolfgang Feist's standard explanation for why 0.6 ach50 is a Passivhaus requirement. Dr. Feist has made the statement at least twice.
You can hear Dr. Feist's statement in a video posted on this site:
http://www.aecb.net/feist_videos.php
The relevant section is in Part 2 of the video:
Q. “The Passivhaus standard has a maximum air leakage of .6 air changes at 50 pascals. … In a warmer climate such as the UK, slightly warmer than Germany, would it be possible to raise this?”
Fesit: “No. Not at all. The airtightness is one of the things that we really have to stick on in almost all climates. There are only a few climates where this might not be a [requirement], but very few -- like in San Francisco. In San Francisco you might not need to have it airtight, but in almost all other climates you need that. A major part of the airtightness requirement is to avoid structural damage. You have bad indoor air with humidity, and if there is an exfiltration through the construction you get really big problems of condensation in the structure. This is the major reason to make it completely airtight, and even in subtropical climates and of course in tropical climates, it has to be airtight because you get structural damage without airtightness.”
Dr. Feist made a similar statement when I interviewed him in Boston. My interview is posted here:
https://www.greenbuildingadvisor.com/blogs/dept/musings/conversation-wolfgang-feist
Dr. Feist said, "That is the most important reason it has to be airtight, to avoid problems due to structural damage from moisture. The structural damage problem is the reason why the airtightness requirement is a separate number. That was one of the experiences in very early superinsulated houses — there were often problems, structural problems, from condensation."
reply to Albert-
No, the $1000 was not an estimate of the cost, but just an example to make the point that air sealing down to some threshold may or may not be cost-effective -- it would depend on the cost being fairly modest because the extra energy savings are small at best.
There are also side issues like the ability to use exhaust fans (kitchen, bath, dryer) in a house at 1.5 ACH50 without creating very high negative pressures compared to a house at 0.6 ACH.
Wow, what a great response to my question. This prototype was built in Asheville, NC which is humid and predominantly a heating climate. I used Eco-Panels PU SIPS for the walls with ZIP as the exterior skin and ZIP sheathing for the roof--with of course ZIP tape. The roof deck, band and sub floor were sprayed with Demilec Agribalance and the crawl is sealed with a vapor retarder and has a stand alone dehumidifier with drain to the outside. After the shell was erected and the foam sprayed, all I did was take several tubes of low VOC caulk and run a bead everywhere I could think of. This extra caulking took about a days worth of work and maybe $20 in materials. This house was not to be PH certified, but I was aware of the PH blower door test requirements. Obviously the design was very simple and easy to air seal affectivley. I run a Venmar Constructo ERV on intermittent cycles when the windows are closed. Thanks for all your responses as I continue to learn from other professionals on this website.
Craig Payne
Martin,
Yes. Now I see the origin and point of the statement. if there is air infiltration (or exfiltration) into the wall, then the water vapor traveling with it will accumulate. I'm so focused on Walls systems with an increasing diffusion gradient to the exterior, that I tend to ignore the issue since the diffusion gradient is there to allow accumulated water vapor to dry out of the wall.
I can see a point that if the interior and exterior layers have low permeability, then air infiltration will cause moisture accumulation which then will not have the ability to dry out because of the low diffusion rate. Remove the air infiltration and the problem largely goes away.
This could be an issue with your favorite double stud wall if there was impermeable exterior foam used. That combined with increasing layers of interior paint over time could lead to what he is illustrating as a problem: Taking a wall designed to dry... But with occupants and time, it changes... Becomes less permeable with more coats of paint, and possibly more "leaky" at the interior air-barrier.
That scenario would lend to more moisture accumulation in the wall cavity from interior pressure drive. Again, remove the air infiltration and the issue goes away.
It seems he is quite serious about this. If he is wrong then houses are getting sealed beyond necessary (your point). On the other hand, if he is right and the higher leakage rates can, a do, cause structural damage over time, then there are an increasing number of wonderful superinsultaed envelops that could be at greater risk than initially thought.
I take it that the collective experience in the US & Canada is that we have not seen significant structural damage in "late model" superinsulated envelops. At least not damage that is being attributed to moisture accumulation by air infiltration.
It could be an important point to pay attention to. As ADA utilization grows, the drywall layer is one that could change easily by owner occupation in both permeability and leakage.
Hmmm.
Reply to Michael,
I agree and understand the question about cost effectiveness. In reality and in looking at just energy, all air-sealing improvements are good improvements. The more the merrier. It's only sad :( when none are taken. I'm working and developing strategies that will take a project down below 1 for near the same money as 1.5. At least thats the trend so far... The hope is that really tight (pick your number) becomes common just because it's simple, inexpensive, and accessible.
As far as vents and other penetrations... They are a separate issue and a separate set of choices. My issue is simply envelope quality and integrity.
Albert,
Moisture accumulation in walls is, of course, a serious matter of concern, and has been for 30 years. Ever since WUFI was developed, builders and designers have a good tool to see whether a proposed wall design accumulates moisture at a faster or slower rate than the wall dries out.
Exterior foam, if properly specified, lowers rather than increases the chance of moisture accumulation in the wall, because the exterior foam keeps the sheathing above the dew point.
Dr. Feist's contention that the air leakage rate of a home is the major factor in determining when moisture accumulation threatens the building's structural integrity is a gross oversimplification. The building's air leakage rate is only one of a great many factors that govern whether moisture accumulates, and whether accumulating moisture causes any harm -- and most of the factors are more important than the air leakage rate.
Other factors include:
-- where the holes in the envelope are located;
-- the drying rate of the wall and ceiling assemblies;
-- the temperature of vulnerable building components in the walls and ceilings;
-- the vulnerability to moisture of the specified materials (for example, OSB is more vulnerable than concrete);
-- the climate (including rainfall, temperature, and RH),
-- and many other factors.
Martin,
I assumed that your "Favorite wall" (double stud) would most likely NOT include exterior foam... eh?
John,
I've said it before, and I'll say it again: I like double stud walls with plywood or diagonal board sheathing. Such walls don't need exterior foam.
But I also like 2x6 walls with foam sheathing. Both types of wall work well.
Believe it or not, it's possible to note that the Yankees are a skilled ball team, and the Red Sox are also a skilled ball team. You don't have to choose sides if you don't want to.
John,
I love it that you put the siga comic up on the post :) They used to print and distribute it, but no longer because they admit that it's a bit "kitchey" these days. Maybe we can see a new one some day. I'll put up the whole PDF up here at http://www.smallplanetworkshop.com/library/ in case anyone can use a full copy. Perhaps it might be helpful to some builders as a tool to explain some basic building physics to potential clients. Pardon the embedded sales pitch. It pays the bills...
Martin,
The irony is that Linda Whaley had just posted her weekly blog entry on our website on the new features in WUFI BIO. And Here I am totally missing your point on Dr Feists concern about air-sealing relating to building damage. Regardless if whether one considers it an exaggeration, I'm going to hear about my own ignorance from my co-workers for quite some time... There is nothing like public self destruction... For those interested in a WUFI BIO snapshot: http://www.smallplanetworkshop.com/small-planet-blog/.
Craig Payne,
It's great to see more examples of voluntary air-sealing that appears to be quick, affordable and reasonably painless. Your efforts and success will be valuable to others. Nice work.
I mentioned a house over on JLC that was recently tested at 0.1 ACH @ 50 Pascals.
I am working on the house currently - (nothing fun, just drywall) but it is interesting house to look at.
It is in SW AK - zone 8. Double wall with 26" between exterior sheathing and interior sheathing. That space is filled with cellulose - interior 2x4's even have batts in it. Walls are over R100, roof is over R150 (if I am remembering right).
It has one triple pane tilt and turn door. 2 south facing tilt and turn windows and one north facing (view) triple pane picture window. Interior space is about 20' x 20' and it has a half loft with cathedral ceiling starting at 5' and peaking at about 8 feet.
It is pretty amazing, I am finishing a smooth coat for the walls and only have a little space heater and the mud is drying amazingly fast. HRV has been on high and the interior temps are well over 70 withe the exterior in the high 40's today with 25 mph winds....
This was owner built and nothing too fancy was used in making it air tight - just a huge amount of attention to detail and air sealing. They said they set the blower door testing to 80 pascals and only found leaks at the 4 corners of each window and one pipe to the exterior. The had nice headaches after a few hrs of that.. :)
Gas here in SW AK just jumped $1.50 with the first shipment of the spring and is over $8.00 per gallon. Electricity is around 0.40 KWH after a local AK rural power subsidy.
The only heat in this place will be 21 CFL bulbs and a very low wattage electric wall heater....