# Insulate basement header with imbedded joists???



## 97catintenn (Sep 29, 2007)

My guess as to why it is unwise to insulate where wood meets concrete, is due to condensation. The concrete being cold and wood being warm creates condensation and it needs to be able to breathe. If you insulate it, you will trap the moisture in and it will rot the wood.

I just saw this on Holmes on Homes earlier this evening, lol.


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## AtlanticWBConst. (May 12, 2006)

lackofunds said:


> Any suggestions about what I should do to insulate these embedded headers??
> Thanks,
> lackofunds


Hopefully all that imbedded wood is pressure treated. Judging by the age of your home, it may not be. If it is not, your best bet is to not touch it, for the reasons that the previous poster listed.
If it is PT, then you can use ridgid foam board attached with construction adhesive and galvanized fasteners (nails or screws)


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## chris33 (Oct 18, 2007)

Natural Resources Canada - Office of Energy Efficiency has helpful information on insulating basements (http://www.oee.nrcan.gc.ca/residential/personal/new-home-improvement/choosing/insulation-sealing/basement/khi-inbasement.cfm?attr=4).
They recommend not insulating the joist spaces where joists are embedded. Air sealing these areas is recommended.
I am about to insulate my 100 year old house which has embedded first and second floor joists. I guess the only way to totally insulate the exterior walls is to apply insulation to the exterior but I don’t want to cover up my brick.
Any other ideas on how to maximize insulation while protecting the embedded joist ends from rotting?


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## cabber24 (Dec 2, 2008)

Does it matter if the joists are above grade or not? Would spray foam work? or is that a bad idea too?


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## mwh (Jan 2, 2009)

*embedded joists*

i have the same issue. i can't see why if you properly vapour barrier or use spray foam so there is no chance of moisture becoming trapped that it is a problem to insulate between joists. unless they're scared moisture is coming in via a crack in the foundation?


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## JCAHILL4 (Nov 3, 2008)

The joist are going to pick up ambient heat from the house and transfer it down the length of the joist to where they are embedded, where heat meets cold it will create moisture. Spray foam or vapor barrier isnt going to matter, therefore they will need to breathe.  Some times 100 yr old houses suck.


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## Wildie (Jul 23, 2008)

Hmmmmmmmm! My daughter has an older home that has a standard box frame construction! At some point, some enterprising sole filled the joist cavities with house brick! Mortared in place! I installed rolled insulation from the sill plate down to the 4 foot mark! ( it came with attached vapor barrier) Using R12 bat insulation, I faced the bricks in the cavities, and ran the v/b over top! The question is, am I facing the same problem as if the joists were embedded?


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## troyce1 (Oct 9, 2008)

what are embedded joists?


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## Wildie (Jul 23, 2008)

troyce1 said:


> what are embedded joists?


 When the forms are built for the foundation, the joists are put in place before the cement is poured! The cement is brought up to the level of the top of joists, thus filling the joist cavity with concrete! Its my guess that this methed of construction died out in the period of around 1920. At least I have never seen this on newer buildings!


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## mwh (Jan 2, 2009)

*embedded joists*

my joists are embedded in the foundation wall however extend through to the ouside 2x8 end plate, my house was built in '59. because my joist run to the outside end plate they will breathe to the outside therefore it shouldn't matter if i insulate the joist space...correct?


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## Schultz (Jan 11, 2010)

*Embedded Joists in Basement Header, Yes or No?*



Wildie said:


> some enterprising sole filled the joist cavities with house brick! Mortared in place! The question is, am I facing the same problem as if the joists were embedded?



Just like Wildie, I'm facing the issue of house brick mortared in between the joists (which otherwise sit on top of a poured foundation). The whole inside wall is plastered smooth; a quarter inch of plaster top to bottom, finishing the wall from the bricks up in between the joists right down to the basement floor.

I want to insulate the header area, but I worry these are effectively embedded joists.

Is it safe to insulate in this sort of semi-embedded header space? I can understand the moisture concerns... concrete will generate moisture, and wood will hold it. But my foundation runs high up off the ground and there's little hint of any moisture problems anywhere.

I'd like to go for it.


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## Gary in WA (Mar 11, 2009)

Rim joist assembly must be insulated with air impermeable insulation
*Interior air cannot access concrete condensing surface* or rim joist condensing surface due to spray foam layer
Spray foam insulation layer is vapor *semi-permeable permitting inward drying*
Spray foam must be covered with fire/ignition barrier Highlights mine. From under Fig.4: http://www.buildingscience.com/docu...ment-insulation/?searchterm= joist insulation
Another good read: http://www.buildingscience.com/docu...rol-for-new-residential-buildings?full_view=1 There is also one on stone foundation insulation.

Be safe, Gary


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## gregzoll (Dec 25, 2006)

I used Kraft faced R-13 around my basement Rim Joist & header pockets. It has helped a lot in stopping the cold. That along with using Window & Door foam to seal a few cracks between a couple of joints on the sills, and basement window headers. Next year, the windows are getting replaced with more energy efficient, since they have been in the house for over 70+ years, and when we reglazed them last year, used Lexan, because it was cheaper at the moment.


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## policestyle (Dec 3, 2010)

*Insulating Basement Headers...*

This worry about trapping moisture is really a headache, and I wonder if it's even justified. Isn't concrete and brick ultimately breathable to the outside? In that case, doesn't moisture just find its way to the outside no matter what?

I could see if both the outside and the inside surfaces were sealed, leaving a warm wood channel to meet with cold concrete in a locked chamber...

This is driving me nuts because I had an energy audit done (on my 1905 house), wherein the auditor told me to insulate the basement headers. When I went back to him about this "moisture risk", he didn't seem to know/ think much about it.

Are we listening to these Holmes guys too much? Does anyone really know what's going on with moisture/ air/ heat??

Sorry, just venting (a pun in there to make me calm down).


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## fixrite (Mar 1, 2009)

Yes and no regarding listening to Holmes guys too much. If you were to paint the interior of your basement foundation walls with a quality sealant one would think this would be a good thing, but.... the moisture will push the paint off of the concrete and you will loose your seal allowing moisture to find its way into your wall and rot your wood. If you think about how moisture works you will better understand it. If you take a glass of milk...ok beer out of the fridge and leave it on the warm counter it will soon have a layer of condensation on it, much like how your house will if you do the same with cold coming in contact with warm. So the question remains how do you stop the cold from coming into contact with the warm. In your case it would be best to seal from the outside and increase your insulation outside. Sometimes that is not always possible or not wanting to alter the exterior as it adds character of the house. I am only guess on this next part but I would think if you insulated with spray foam ( and there open cell and closed cell foams to choose from) that would be your best choice from what I can gather. Although I have not give an outright solution I hope it is better understood.
cheers


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## marko123 (Feb 3, 2011)

Well, my house was constructed in 1979 and it doesn't have fully embedded joists (with concrete going up to the top of the joist), but mine seem to be PARTIALLY embedded (with about 3" to 5" of space from the top of the concrete to the top of the 7" joist). So, some of my header board is exposed. 

With the energy audit, I was told to make the insulation a minimum of R20. Could I place fiber-glass insulation, cover it with rigid board insulation (totalling R20) and then seal it on the warm side? Will that still invite a moisture problem?


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## Gary in WA (Mar 11, 2009)

The foam needs to be in contact with the concrete. The f.g. should never be in contact with concrete due to condensation, as in the BSC site in my previous post on page 1.

Gary


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## toxin101 (Feb 13, 2011)

*HELP!!* i am also trying to prep for my 2nd energy audit & having a hard time figuring out exactly what 'embedded joists' look like, since the energy audit guy told me to insulate the basement headers but NRCan says not to if joists are embedded in concrete. is there somewhere i can find a picture of embedded joists &/or other types of basement headers?! i started poking around the basement headers & i think someone put batts in some basement headers & covered them with wood planks that don't completely fill the areas, other areas have more batt &/or white styrofoam in the header areas on top of wood planks &/or right up against the outside brick, while other areas are empty & i can see bricks (energy audit guy told me foam crap releases toxins when burn so it needs to be removed regardless of what else is or isn't done here).there appears to be no moisture, air, vapor or other barriers in place anywhere. i'm totally confused. do i remove the batts & wood? do i seal them in place & insulate on top? any help &/or links would be GREATLY appreciated...thank you....


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## RobJ (Feb 27, 2011)

I'm also prepping for my second energy audit and just realized that I have embedded joists too. Here's a picture. Not sure what I can do, the guy at the hardware store recommended Roxul.

Any thoughts? Would Roxul allow the area to breathe properly (if I don't put up any vapour barrier, obviously)?


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## toxin101 (Feb 13, 2011)

*insulate bsmt header w/ embedded joists: (UNVERIFIED) IDEA*

@RobJ - i haven't been back here since i posted my question, so i must have picked up your reply-vibe or something!!

i was at a home show yesterday & the following idea was given to me by 1 of the exhibitors who worked for an eco-energy company & said this is what he would do if hired by a customer to deal with this situation (no one else has been able to help me since i started my search for knowledge): 

1. apply a piece of vapor barrier against the concrete, having it extend away from the wall, & staple on 3 sides;
2. apply batt made specifically for basement headers, compressing it slightly into the area, making sure the vapor barrier extends past the batt on all sides; &
3. optional: cover, primarily for esthetic purposes.

he said this 'special' batt would have added protection against ??, moisture i think. he recommended roxul, but said he isn't up to date on all available products & there might be something better out there now.

i haven't yet searched around to see if the idea is good, useless, or could cause problems. i also didn't ask about whether or not air sealing with foam spray, the NRCan recommended treatment for basement headers with embedded joists, should also be done before adding vapor barrier & batt. my 2nd energy audit is this week, so clearly this project won't get done to qualify for a rebate, but it would be nice to warm up the hardwood floors in the living & dining rooms...


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## Canadian Dave (Apr 17, 2011)

I've been reasearching the same question all day . . . how to handle an embedded or partly embedded floor joist. I found this excellent acticle that discribes the approved technique for imbedded and partly imbedded floor joists. Well worth the read!


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