My 60s vintage ranch in south central Pennsylvania has a cinder block foundation with parging above grade. The lot slopes to the rear of the house so that most of the foundation is exposed toward the rear. It is in need of paint. I would like to apply an inch of rigid foam insulation covered with parging/stucco or similar finish. (I suppose this is a DryVit sort of retrofit.) I am gathering some articles from FHB and also wanted to tap this Brain Trust for recommendations.
Materials? Type of rigid foam?
How to attach the foam to the foundation?
Any moisture considerations?
How to handle edges at outside corners and around door and window openings?
How to select and apply the finish?
Any other info that you need?
Thanx, as always, for your help.
Replies
Personally, I'd maximize the thickness ... 2 inches minimum. If you are going through the tyrouble and expense go for the biggest R-value you can. Expanded or extruded polystyrene, I would think ... extruded has a better R-value at a higher cost (but you pay for what you get). Barring detail problems ... I'd go the max you can afford. You will only do it once.
Thanx. I agree with you in principle. Thickness is the issue here. I can't have the foundation thicker than the siding above it.
Put an angle on the top of the insulation like they sometimes do when pouring concrete slabs against rigid insulation. That way there is no interference with the siding. Or make a bump out with an angle on top of the insulation like you see sometimes on top of stone foundations it would look like a cap.
To get you started: http://www.senergy.cc/documents/details_pdf/1026918_ICF_details.pdf.
Hey, thanx Marson. Just what I needed: details and specs.
What do you think about Perolite in block I have been told it will hold water is this true?
Better than nothin' ... but not much. Personally I've never been a big fan of insulating CMU (concrete masonry units) ... I've done a lot of studies and reading on the subject. Are you thinking new block or existing? Retrofitting existing can be difficult. New, I would consider the CMU that is designed with an integrated foam insert that minimizes the thermal bridging while still allowing maximum bond beam use. That is the best system I've seen, but it still tends to be thermally iffy ... in my opinion. Again, if that is the only choice, that'd be the way to go.
I have the block up for a daylight basement and need to insulate some how Now I am waiting on the trusses to be built so the cells are still open . suggestions poly foam ?
you could do e.g. 2" of blue/pink board on the exterior. Have flashing bent up for the top ... like the other guy was saying bend it up, 45, and then up under siding. This is a nice/reasonable detail; gives the foundation more of a visual base for the house, I think. Put the waterproofing on the CMU first. Downside is you are still looking at finishing the inside. Not sure if people would recommend gluing drywall directly to the CMU here. Upsides are insulating the outside of the mass (arguably the better choice) and minimizing how much space you lose.
Or you could do the inside w/ framing and batts or do the 2" of foam there, too. I think some people might glue it on the inside ... including the drywall. Most, I suspect would furr out, insulate, drywall. I personally would do rigid blue/pink board. I recently did one by cutting 2" top/bottom plates, 2x2 framing, 2" foam, and drywall. The plates keept the rest of the framing off the wall. The foam insulation minimizes how much space you lose.
I'm sure others are going to jump in with good opinions and/or experiences
sorry ... didn't read/respond to your question. No ... can't do block foam inserts ... they must be done while the block is being laid up. Perlite ... is best also done during layup. You can't guarantee the perlite will flow everywhere you would want it.
Insulating and flashing the outside is very straight forward ... see my other response for detailed discussion on that.
Thanks for the info, I do not want to insulate on the outside because finishing it. I think it would be easier to stucco block. What about just gluing the blue/pink board to the wall on the inside. Perolite is about 1000 $ to fill a 1500sf basement i just wander how well it works. This is new construction by the way ..
personally, I think perlite ... and generally insulating CMU unless planned PRIOR to layup is a marginal endeavor. You just don't get good thermal quality. There are way too many thermal bridges ... not to mention the bond beams (horiz and vert). If the wall is already done, it's even more iffy to make sure you get it to the bottom row.
I'd insulate the inside ... get some opinions re: glue up vs. insulation and furring strips.
FYI ... you buy a roll of colored flashing ... have it bent to shape and that is your exterior finish ... that is if you just have a few inches at the top. If not, you should be able to stucco exposed exterior no problem.
you have to do some kind of detail at the top if you go with exterior insulation
i dislike exterior insulation.. we always stud the interior and add insulation there