attic insulation and air-sealing
pulper_11
| Posted in Energy, Heating & Insulation on
Hello:
I had an energy audit performed on my home in southeast michigan. the company that performed the audit made some recommendations. Since then I’ve been doing some research to better understand this and have some questions.
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The blower door test showed that my house was about 3 times more leaky than it should be. the auditors showed me the thermal imaging pictures where a lot of the leaks were coming from. they suggested some relatively simple fixes that i should be able to do (caulk around the trim of the windows, caulk between the baseboard and the floor, weather stripping the doors). however, details regarding air sealing the attic (other than the attic hatch) was not provided although based on the imaging pictures it is definitely needed.
The amount they gave me included blowing cellulose in the attic to R-50. however, i did not see any air-sealing for the attic. when i emailed them to confirm, they simply said that air sealing the attic was not included. i would have thought they would then have given a price on it but they didn't.
My question here is:
For a company who's prime business is insulation and energy conservation, do you think that they should be performing insulation of the attic without ensuring that it is air-sealed first? it doeesn't sound right to me, but perhaps the cellulose is good enough.
thank you.
Paul
Any air that escapes into the attic through even a good blown job will be a $ loss to you. Further, you may still experience ice damming and the resultant damage that it can do. I think detailing the leaks is an important measure. Adding a foot of celulose, while limiting the amount of loss probably won't eliminate it entirely. Once the foot of cells is in, it will make air sealing that much more difficult.
Any can lights in the ceiling-they are a bit opening. Wire runs and vent pipes are another. Not vented to the outside bath exhausts speak for themselves.
Best of luck.
i just saw your post, i got an offer from my natural gas company Nicor Gas in northern Illinois; they will rebate $600 for attic insulation and $600 for air sealing. i looked into air sealing a year ago, there was a segment on Hometime, it's not cheap about $3000. But I'm sure it would change your life, better air flow, save money, better return air, make your house less dusty. I don't know that it would ever pay for itself. thanks, douglas
Air sealing ceiling leaks is definitely important. But it doesn't get done because it a sunuva beech to do. Most of the leaks are out near the eaves and freakin impossible to get to in a low-pitch attic. And that's BEFORE any insulation is blown in. After insulating fugidabodit.
the air sealing I'm talking abouit is foir your ductwork. It's a chemical blown in process.
My house is 35yrs old and there's plenty of leaks, i like it that way, your house can
be too tight, a friend of mine his new house dripped condensate in the winter, too tight
no new air. thanks, douglas
douglas
Could you fill in a bit on the too tight house that dripped condensate in the winter? That's a broad statement that doesn't usually hold water.
sure, my friend had a new house built, semi-custom two story. He had the contractor take every
measure to ensure an absolutely leak proof house, air leaks and heavily insulated. This was in the
days before energy effecient furnaces, make up air was provided internally. in winter, the exterior walls
were wet, no humidifier in place. thanks, douglas
douglas
With the info you provided I think it's a stretch to come to the conclusion that a leaky house is a better house.
Assuming you are correct, what did your friend do to alleviate the problem.
And where in the country was this drippy house built?
attic air sealing...
I have quite a bit of experience in this field and i seem to be addressing it with homeowners on a very regular basis.
Having been certified as a home energy auditor and having worked in the business for several years I can tell you that the importance of attic air sealing is more significant for energy savings than the insulation is.
The two procedures really complement one another and should always be performed in sequence...air seal and then insulate.
The use of high levels of blown cellulose does actually accomplish quite a bit of air sealing in the attic but it is always best to perform an air sealing technique prior to installing the cellulose.
If you must use fiberglass roll or batt insulation then the importance of accomplishing attic air sealing becomes more important as that insulation is very poor at achieving any effective air sealing.
Attic environments are not nice or easy places to perform retro air sealing and that creates problems with doing it properly.
Many of the thermal breeches, or holes to the conditioned spaces below the attic are difficult to reach and they are not all visible in an attic where some insulation has already been installed.
You need to look for the most common breeches such as recessed light cans, plumbing vents, pull down door openings and the biggest of them all-a masonry chimney penetration.
If you get an effective air seal at these areas and then install blown cellulose at the proper depths required by your local code or above any existing insulation already present in the attic you will achieve a significant reduction in the blower door infiltration/exfiltration reading and also a significant reduction on the thermal imaging of the breeched areas.
In new construction or in attics free of any insulation I only recommend the use of sprayed closed cell polyurethane insulation.
You can find plenty of information on how to air seal the thermal breeches I mentioned above online by doing a word search for attic air sealing. The procedures are not complicated but take care to use proper safety precautions against contact with existing insulation and attic dust.
Make sure any recessed light cans are rated IC for insulation contact if you plan on covering the cans with insulation.
Be careful with the recessed cans though-some are rated better than others at air sealing and they all leak to some extent. Alternative measures of insulating/air sealing the cans are available.
i do not recommend relying on any energy or insulation company to achieve proper air sealing without dilligently monitoring their work regardless of what they tell you. Don't sign a contract for attic insulation if it does not address the topic of air sealing-one way or another.
Attic air sealing is essential for proper insulation performance. educate yourself about it and you will be in a better position to have your attic insulation give you the benefits it should!
You omit one common major source of air leaks: Drop ceilings. Unless installed correctly, they leave large areas of the adjacent studwalls open to the attic,
drop ceilings....?
I am not sure what you mean by your comment about drop ceilings being a source of major air leakage into the attic space.
I have never encountered that kind of problem in the hundreds of energy audits I have conducted.
Would you please explain in detail what you mean?
thanks.
Thanks for the extensive comment here! i appreciate it. i talked with the company and they informed me that the reason they didn't quote on air-sealing is that it would be $300 for them to do it and i could do it for about $20 (can of great stuff). my house isn't big so there's not a huge amount to do and not a lot of interior walls where the top plates need to be done. he went over with me what needs to be sealed.
i think this makes sense although i would have preferred better communication earlier, but i am at least partly to blame for that too.
thanks everyone for your comments.
pab
attic air sealing pt 2!
I am happy to have been of some assistance.
I still recommend that you research online the attic air sealing procedures and techniques.
Not much to it but it is labor intensive-dirty labor performed while crawling across ceiling joists!
Be sure you know how to move around in the attic so that you do not cause inadvertant damage to the ceilings below the attic space.
Make certain you wear protective clothing-work clothing-and use a cartridge style respirator. The nuisance dust masks are not adequate breathing protection.
Be gentle when moving any existing insulation when you are accessing the thermal breeches you want to seal.
I suggest one more time that a company selling energy conservation measures should include attic air sealing as the #1 energy saving procedure. Failing to do so and consequently stating that the air sealing is additional cost is not good energy saving procedure.
The air sealing in the attic space is the most important aspect of any energy savings procedure in a house. Please be vigilant of any such company.
By the way-if you are going to attempt the air sealing on your own Ialso suggest that you consider doing the blown cellulose installation as well. It is not anywhere near as time consuming or difficult as the air sealing and you would save yourself more money and gain more satisfaction if you did it.
Please let me know what you decide and how you make out with your project.
Good luck!
air sealing above dropped ceilings...
Thanks for the reply but I still don't know what you are referring to.
I have been working on houses for 50 years and in my part of the country I have not ever seen a condition such as you have attempted to describe.
What part of the code are you referring to...section/sub-section please!
The only situation I can imagine that would fit the description of the ceiling/stud wall condition you have described would be in a house built with ballon framing-possibly. That building technique has not been used around this area for a very long time-since way before my tenure began!
Please reply with a sketch if possible of the situation you are trying to describe-and be more articulate in your description.
What is the framing situation you are referring to with a coved ceiling?
Thanks!
k,
I think he suggests the way most soffits are/were built in kitchens, baths over tubs/vanities. Frame then sheetrock-so walls are open to soffit and then to joist system.
Take one hole through a plate/floor into the basement and it feasibly could travel uninterupted and even redirected, right up to the attic.
air sealing...
Well, in my original reply to the post about getting a quote for attic energy savings work from a member I was explaining the basics of attic air sealing.
My post is self explanatory-not having been intended to be a complete dissertation on the subject!
I mentioned some of the more common large thermal breeches to be aware of and then suggested he educate himself online more thoroughly about the details involved with attic space air sealing.
The reply I got to my first post is what is being discussed now and I disagree with the poster's remark about having ballon style framing resulting in large thermal breeches into the attic space as a common modern framing condition.
I would be happy to discuss in further detail the details of attic air sealing if you are interested in learning about the subject.
I am extensively experienced in that area and will address any framing situations you might have questions about but please include some kind of sketch of the framing so I can each condition you are inquiring about.
You made reference to stud cavity air movement in your post...that is another area of concern and can affect the attic air sealing procedure.
Please remember when discussing air sealing in a house-the object is almost always to reduce the infiltration/exfiltration measurements of air movement as indicated by a pre and post blower door test.
The procedure is to seal the larger thermal breeches first and work towardssealing progressively smaller breeches as far as is practical
Thanks for your interest and contribution to this post stream!
It's not balloon framing, though that would certainly make it worse. Just standard construction techniques used in the Midwest from about 1960 to 1985 or so.
that is not
a common framing technique here in the NE.
It may exist in this area but it is certainly not common as you stated in your first post.
Fire blocking would be necessary to satisfy our version of the IBC if this was done in this part of the country, although I can't see why anyone would want to do that framing detail in our climate!
kxm
I was just trying to explain what I think dan meant with what he called "drop ceilings"............was a soffit or bulkhead framed in kitchens and baths (and not being sheeted or firestopped b/4 drywall). These open runs can take air source from one place and allow it to continue and appear in an entirely different place. I'm just a dumb carpenter.
I like your expertise and hope you return often-there's always room for someone that both knows the methods of energy audits and the solving of the problems that are sure to exist.
Don't be a stranger, and welcome to Breaktime.
yes calvin...
I realize what you were trying to explain...and thanks to your posts-and dan h's last one I now believe I know what he was trying to describe.
Thanks for joining the stream!
I too am a carpenter by trade-grew up in the renovation/remodeling/repair business, having worked with my father since about age 10.I have ventured into many different areas of construction over my career but have by far the most experience in the residential sector.
My experience in home energy auditing grew out of my extensive residential experience and I enjoyed it.
I do have a certification in that field and as I posted previously I spend a good deal of time lecturing on the subject of air sealing and ventilation/insulation in attic spaces.
I also am constantly trying to get people to do other no brainer energy saving procedures within their homes-like converting to demand hot water equipment for both heating and potable supply.
Currently I am battling the false advertising claims that energy saving companies are making quite often around my area.
I was drawn into this post stream because I was astonished that the fellow who began the stream had been told by an energy savings contractor trhat air sealing his attic was going to be $300 additional cost and was not even addressed in the original proposal!
I repeat-air sealing, insulating and ventilation are all necessary in an attic space if you wish to achieve an effective reduction in the air infiltration/exfiltration rate of a house.
There are other measures to take to help reduce those rates in other areas of the house, but in the attic those three procedures complement one another so weel that they are considered to be a total system by knowledgeable energy auditors.
Thanks again for your input.
kx
Interesting how topics pop up in other venues at about the same time.
This from JLC:
Yup, page 70 is what I was talking about: http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/TBC_Guide_062507.pdf
energy star manual...
thanks for the link danh...a picture is worth a lot!
the photo on page 70 does not show clearly if there is fire blocking installed below the soffit-but the insulation in the sidewall does extend to the bottom of the soffit so it may or may not have fire blocking there.
diagram 5.3.3 below the photo does clearly show fire blocking installed below soffit.
the fire blocking would definitely impede any air flow within the stud cavity.
the photo does show recessed light cans protruding into the soffit cavity-and thet are a problem for certain!
blown cellulose above the soffit-filling the entire soffit cavity up to the same level as the cellulose in the attic space would achieve a great deal of air sealing and achieve the insulation at the same time.
as long as there is fire blocking installed below bottom of soffit to support the cellulose.
thanks again!
What you take to be fire blocking in 5.3.3 is the nailer for the drywall, and it may or may not be there (probably not). And it's fairly plain in the picture 5.3.1 that there's no fire blocking other than the fiberglass (which would only be present on exterior walls).
Cellulose will cut drafts some, but is no match for the draft set up by a 100 degree temperature differential.
i disagree
with your comment that the cellulose will block air flow "some".
It blocks a lot of air flow!
I have not been discussing energy star rated techniques here dan-only basic air sealing-and i have a lot of experience with that.
as far as the photo showing clearly that there is no fire blocking-I disagree again-I can not see what is above the stud cavity insulation at the bottom of the soffit. Some insulation is visible within the soffit but is falling away.
You can call the fire blocking which is visible in the diagram a drywall nailer if you like, but it is not necessary at that location to carry the drywall as the diagram indicates 16" oc framing. If it were 24" oc framing in the wall then I would certainly want blocking at that location to carry the drywall.
Whether it is a fire block or a drywall nailer-it produces the same effect as fire blockinbg as far as impeding air flow in the stud cavity.
And I have a lot of experience with 100-degree temperature differentials.
what exactly is...
...your supposed experience with 100 degree delta T dan?
where do you live that would require such a delta T design?
your posts thus far do not indicate that you have either the knowledge or the experience with weatherization procedures.
could you please be more specific?
thanks!
wow dan!
MN!!
Well you guys certainly have a much colder design criteria there than we do here (central NY)....and I actually like your idea of using a 100 degree delta T for design because you guys will get 30 below temps sometimes, I know!
I have never seen anywhere near that temp here.
What R value did you put in your attic?
Originally the attic had about 8" of cellulose. This was normal in the 70s. We upped it to about 18" several years back.
great!
How much air sealing did you do-if any-prior to adding insulation?
I sealed a lot of wire and pipe penetrations, taped over holes in ceiling fixture boxes, closed off the soffits in the kitchen. Coated the tops of interior walls (where I could reach them) with roof coating to seal any leakage around the top plate. And when we replaced the furnace with a power vented unit I removed the flue and sealed that area.
Unfortuntely, there was such a tangle of vent pipes and truss braces over the bathroom I was not able to close off the dropped ceiling there, on one end.
you accomplished a lot...
..of very meticulous air sealing.
too bad about the bathroom area you didn't get to.
how does your house perform?
I've got no real way to compare. But the house is reasonably cozy in winter.
The thing that got me going on the bathroom problem is that we had some bad condensation in the attic this winter (since it''s the first "normal" winter we've had in about 20 years). And the condensation is all located in that one small area.
well dan...
... must be a way you can reduce that thermal breech above the bathroom---how about a large application of expanding polyurethane foam?
I'm working it from the inside now. Gotta close the hole under the steps.
you will get it...
...dan, i know you will.
how about posting some photos as you continue working on the problem?
thanks
i have been doing air-sealing on the main floor but have now shifted my attention to the attic.
in my attic, there are a number of wooden planks on the floor. between each plank are cracks the length of the plank that are around 1/4 to 1/2 inch in size. in other words, the wooden planks are not tight together along their length. the area under the planks is empty for a number of inches so if i use a foam to seal between the planks, there's nothing for the foam to adhere to below the planks and it will, after a bit, just fall through.
could i use air-sealing tape to seal these holes between the planks? i saw in the may 2013 issue of fine homebuilding a long discussion of air-sealing tapes, but this seems to be more for initial construction and i'm not sure if this would apply for what i'm looking to use it for.
would appreciate some thoughts on this. Thanks!
Presumably below the planks is the back side of the ceiling. That is the real air barrier that you want to seal. Pull up a few planks if necessary and inspect the ceiling, looking for obvious air leaks. Then, once you have the ceiling sealed to your satisfaction, consider blowing insulation under the planks.
Thanks Dan for the post. unfortunately this is not really possible in my situation. these planks, while removable from one end where they are nailed to an open joist, are not removable from the other end. They are nailed to a joist on the other end and a wall is on top of that joist. I started to remove one but noticed that this wouldn't be too smart and stopped. The amount they are removable on the one end isn't enough to look underneath to seal.
any other suggestions, or am i just SOL with this?
Thanks!
pulper
If you get yourself an "oscillating multifunction tool" (Multimaster knockoff) you can easily cut through the boards, leaving the part under the wall. With only modest care you can make a pretty clean cut directly over a joist so that the ends will be supported.
Would you have a picture of these planks and the attic space? Are these planks on top of the ceiling joists to make a walkway of sorts? Does the house use trusses or joists/rafters?
I don't think the $300 estimate would seal all penetrations. Have them specify exactly what will be sealed (ex. how many ceiling fixtures, wire penetrations, etc.)
I am planning to seal (air and vapor) up my attic this spring so that I can have more insulation blown into the attic space.
For wires and pipes entering the attic space I hope to seal them with a butyl rubber caulk...seems to stay more elastic than silicon and sticks better. I thought about spray foam but from what I hear it is not a vapor barrier and up here it is important to keep moisture from entering the insulation.
With the ceiling lights I am planning to make boxes using a rigid styrofoam that is foil faced (as vapor barrier). The boxes will be sealed around the ceiling lights using the butyl rubber caulking.
More than the sealing will need to occur before any insulation is blown in but I wanted to post just what I was doing to seal up the attic.
Our experience with weatherization
My son bought an older (early 1900s) 2 story house about 5 years ago, in the fall. The first spring they replaced the double hung sash with retrofit channels and double pane new sash, and also replaced the 4 exterior doors with new prehung insulated steel doors. Their heating bill for the second winter, after doing the doors and windows, was about half of the first winter's bills.
Then they had a blower door test and energy audit done, with recommendations for attic and crawlslpace sealing and insulation. They shoveled out all of the old cellulose from the attic and found that there were remnants of an old attic floor under the insulation, with occassional boards cut out so that cellulose could be put under this old floor. The effect was that there was the ceiling blow, then space with some (settled) cellulose, leaving air space and openings to the edges of the attic, then the old attic floor, then the later addition of cellulose. After taking out the 2 layers of old cellullose and the old attic floor, they used many cans of foam insulation and pieces of foam board insulation to seal all cracks, openings, and leaks. They also removed the old chimney where it went through the attic floor/2nd floor ceiling (it had been removed through the roof some time previously when the house was reroofed years before). After sealing the attic, they blew in about 18 inches of new cellulose and fabricated and sealed a new hatch for the attic access opening. Then they hired a contractor to apply foam to the sill area in the basement and the crawlspace walls. It took 5 or 6 call backs to get the insulation in the crawlspace done to the specs of the contract (they had specified a minimum thickness on all the walls in the crawlspace).
When this sealing and reinsulation was done, their heating bill was about 1/2 of the previous winter's bill, or 1/4 of the first winter's heating bill. And the house is draft free and much more comfortable.
We feel that attic sealing is critically important!
Jim, in western Wisconsin
What likely happened is that the humidity in the house is too high causing the moisture to condense on the windows and exterior walls. In older leaky houses the air being exchanged helped keep humidity levels lower so that condensation occurs less often.
With this house if there is a humidifier on the furnace (forced air) then the level should be adjusted to a level based on the outside air temperature (i.e., the colder it gets outside the lower the humidity setting should be used). I have a humidifier from honeywell that included a chart on the humidity-meter with preferred humidity values based on the outdoor temperature.
With air tight (or tighter) houses, an air exchanger is important. It not not brings in fresh air into the house but it will also remove some of the excess humidity and keep the level more reasonable (moisture should not condense on the walls).
I made some assumptions in posting this but the fix for this specific house depends on a number of factors and likely should be a topic for another post.
Just wanted to give an update. I had the post blower door test performed. With the work that I did and of course the closed cell foam insulation added to the rim joists in the basement, the air sealing reduction was 21.5%.
Not an awesome job (especially when you read all the homes in fine homebuilding that get down to below 700 on their blower test) but I went from 2540 to 1995 and I'm happy that at least my work has been objectively verified.
Thanks everyone for your posts and your help. I'm not done at this point but am going to certainly take a break from this work and move onto something else.