This year, I’m thankful for closed-cell foam insulation. Yeah, that’s right.
November 22nd, 2011 | 16 comments
Yes, you read that right. I’m thankful for closed cell foam insulation. Of course, I’m thankful for my family, health, and all that other jazz, but this is a blog about home inspections and home related topics, so I’m going to stay focused on that. To fully explain why I’m so thankful for closed cell foam insulation, I first need to complain about my house a little bit.
My thirteen-year-old Maple Grove house has an unfinished basement with a walkout; this means about half of the basement walls have a poured concrete foundation, and the other half, the part that’s above grade, has conventional 2×6 wood framing. The foundation walls are insulated at the exterior with rigid foam; this is a great way to insulate a foundation, because it means that the concrete walls will be relatively warm, and the potential for condensation problems will be minimized. If you want to read more about foundation insulation methods, click this link – foundation insulation.
The stud walls, on the other hand, were insulated the same way as 99.9% of the houses in Minnesota – with fiberglass batts. Yuck. While this is the standard way to insulate a wall, it’s also probably the worst acceptable way to insulate a wall. The photo at right gives a great example of how fiberglass batts are installed incorrectly all the time; just look at those gaps around the junction box. I’ve already dedicated a blog to complaining about fiberglass batts, so enough on that topic.
In addition to having fiberglass batts for insulation, the vapor barrier in my basement was basically useless. Here’s how a vapor barrier is supposed to work: to prevent air from passing through the fiberglass insulation and creating moisture problems in the wall, a vapor barrier gets installed. This consists of 6 mil polyethylene sheeting (aka ‘poly’, aka ‘Visqueen’) that has been made airtight; that means caulked, overlapped, sealed, taped, etc. On a home built today, this will be done quite well. On a house that’s thirteen years old… no way. The vapor barrier will probably be just about useless.
Unsealed vapor barriers create heat loss. Just thirteen years ago, vapor barrier were never sealed. It was standard practice to just use a stapler to throw the poly on the walls and leave everything completely unsealed. This practice allows for air to constantly circulate within the fiberglass insulation, creating a convective loop, which means a lot of heat gets lost through the walls.
I have my ‘office’ set up in my unfinished basement, so I spend a lot of time in the basement. During the winter it gets very cold in my basement, despite the fact that I have 2×6 walls filled with fiberglass insulation. Last winter I kept an electric space heater under my desk to keep my toes from turning in to icicles.
Fiberglass should never be used at rim spaces. The rim space is the area between the floors of a house; this is an area where it’s nearly impossible to install a proper vapor barrier. Without a vapor barrier, condensation can occur at the rim space, creating mold growth or eventually rotting out the rim space. This is why fiberglass insulation should never be used here. On new homes, it never is. The only type of insulation that gets used on new construction homes in Minnesota is closed cell spray foam insulation; we’ll come back to that in a minute.
Unsealed vapor barriers can lead to mold growth. When a vapor barrier isn’t sealed and air is allowed to freely pass through the wall, what happens when warm, moist air hits a cold surface? It condenses. My basement stays relatively cool and dry throughout the year, so the vapor drive is really happening from the exterior during the summer. The walkout part of my basement faces south, so this part of the house is where I have the greatest temperature differential between the exterior and interior of the walls.
During the summer, as humid outdoor air passes through my walls and hits the relatively cool vapor barrier, the moisture condenses. This summer there was never enough moisture to actually drip down to the floor, but it was enough to leave drip marks in the insulation and allow mold to start growing between the insulation and the vapor barrier. This wasn’t major and I don’t have mold allergies, so I wasn’t too whipped up about this… but I couldn’t allow this to continue.
Enter closed-cell spray foam insulation. To address all of the insulation, mold, and vapor barrier issues at the same time, I had the wood framed walls in my basement completely re-insulated about three weeks ago. I had the vapor barriers removed, all of the fiberglass insulation removed, and closed cell foam sprayed in to the walls and rim spaces.
I love it. Closed cell foam acts as a perfect vapor barrier after 2″, it doesn’t allow for convection, and it has a much higher insulating value than fiberglass. Now when I walk down to my basement, I don’t feel a drastic change in temperature; my basement is only about two degrees cooler than the rest of my house. I can sit here at the computer without a space heater, and I no longer freeze my toes off. Life is good.
Having foam insulation sprayed in to the walls was expensive, but it was worth every penny. Will I ever get a payback in energy savings? I’m not sure. I didn’t even bother to check the numbers, because my main motivation for this project was comfort. Saving energy and not having mold growing inside the wall cavities is just a bonus.
Happy Thanksgiving.
Reuben Saltzman, Structure Tech Home Inspections - Email- Maple Grove Home Inspector
Reuben
November 22, 2011, 10:50 am
I see the roll of duct tape on your desk. You must have been doing some plumbing work too, right?
Reuben Saltzman
November 22, 2011, 11:07 am
Good eye! Yes, I was using the duct tape to patch a leaking water heater. Duct tape is good for more than just leaking water pipes
Stacy
December 12, 2011, 6:29 pm
Question: We recently found out we had a major mold problem in our finished basement apartment – where my husband and I sleep. We had a waterproofing/remediation company demolish everything down to the studs, remediate, and put in a waterproofing perimeter system on the inside (exterior) walls. They have now put a vapor barrier from the ceiling down to the floor into the perimeter system (which is now cemented). My question: Is it ok to put closed cell foam over the polyeurethene vapor barrier??
Insulating A Rim Space | Structure Tech Home Inspections
December 13, 2011, 4:58 am
[...] at is the rim space. I mentioned this a couple weeks ago when I wrote my post about how I had my entire basement re-insulated, but today I’m going to focus on the rim space alone and discuss the different options for [...]
Reuben Saltzman
December 13, 2011, 5:18 am
Stacy – I can’t think of any reason why not.
Tim Smalley
December 13, 2011, 10:21 am
Back in the late 1970s, I went to a basement remodling seminar at Knox Lumber (remember them?) in Duluth. The guy – who also moonlighted as a city building inspector – said insulation on basement walls should only go down a foot or so below grade to allow for heat to escape through the block. This was to keep a thawed slurry of dirt against the block to prevent frost from pushing in the basement walls. Was this EVER true???
Reuben Saltzman
December 13, 2011, 3:32 pm
Tim – I honestly don’t know. It’s funny, I just got off the phone with a home inspector in Seattle who was asking about the same thing. It makes sense… but I think that if water management is proper, the frost issue shouldn’t be a concern.
Charles
December 13, 2011, 3:50 pm
Hi Reuben, being that other inspector in Seattle, I would like to reiterate that it always comes back to proper water management—for so many things related to our homes:) The forces of frozen earth against a foundation can be extreme—it simply cannot be allowed to happen and if that means loosing heat from the basement to prevent it, I guess that is what has to happen. I would hope that this would NEVER be a consideration in new construction and that proper drainage and fill materials would be a given.
Insulating your basement? Start with the rim joist. « About Fiberglass Construction
December 14, 2011, 7:34 pm
[...] at is the rim space. I mentioned this a couple weeks ago when I wrote my post about how I had my entire basement re-insulated, but today I’m going to focus on the rim space alone and discuss the different options for [...]
Dustin
December 22, 2011, 7:55 pm
From my understanding- with the exception of the rim joist, it is not permissible to have exposed spray foam insulation as you have pictured in your unfinished basement due to flammability. Is this correct?
Reuben Saltzman
December 26, 2011, 4:40 am
Dustin – correct. The spray foam will all need to be covered over.
TE
April 1, 2012, 2:31 pm
Mold detected behind my vapor barrier in basement after removing sheetrock. Also existing poly -non sheetrocked previously has same small dots of mold all over the insulation and discolored marks (mold about to happen). .
Is this also going to be present in the upstairs?
(which is entirely finished)
Basement has no cold air returns and walls leak air really bad. How to remedy ?
Plan – Installing gutters, removing insulation, sealing wall with something?
framing walls, installing cold air returns along center of basement length.
pulling all windows, re-wrapping and installing with new J channel and actual flashing this time.
I just want to do it right. Should i be investing in closed cell for block knee wall and open-cell for upper wall? Should i vaporlock the buildrite 100percent and seal the block with cement water stopper stuff ?
Please and thank you !
Sincerely, Terry.E
Reuben Saltzman
April 3, 2012, 7:09 pm
Hi Terry,
I’d love to just throw out some answers, but the correct answer needs to be a holistic one that takes everything in to account. You would do well to hire someone to inspect your house to figure out what caused the issues and what the best repair would be. All I would really be doing is guessing. Sorry I can’t be of more help.
- Reuben
Earl
April 15, 2012, 11:42 pm
We have a small rental house with a mold problem. The lower area (3′)of the exterior walls are cement block. The inside has sheetrock directly over the cement block. We have condensation and mold on the lower part of the walls. We want to correct the problem. Our plan is to remove the moldy sheetrock, cover the cement with 2″ closed cell rigid insulation and new sheetrock. Is this a good plan to eliminate the problem? The house is in Lewiston, Idaho. Would appreciate good advise.. Earl
Reuben Saltzman
April 16, 2012, 4:10 am
Hi Earl,
I don’t much about how houses work in Idaho, but if you’re getting mold on the walls as a result of condensation, your plan might work.
TE
April 23, 2012, 12:06 pm
Now my knee wall is just block and 6ml Poly, studs, batting and sheetrock.
Before it was poly on the block and sheetrock side of the stud knee wall.
No moisture or mold grew in between this vapor-locked section.
The mold spots were showing up 1 to 3 feet below the rim underneath the sealed poly.