Foam in Cinder Blocks

Please ignore: cost, time, and the fact that this will be over engineered.

Are there negatives or possible problems with drilling a 1/2" hole in each of the 2 cavities in each cinder block in my foundation wall and filling them with spray foam?

Thanks!

 

The cores cannot allow drainage downward to the drain tile system if you have one.

Minimal increase in insulation in an area that does not need much insulation because of the normal soil temperature from the thermal inertia and heat below. Most people over-think basement insulation and it becomes an obsession.

Dick

 

What is your objective, moisture reduction or insulation? Moisture, no help. Insulation, marginal as the conduction through the rest of the block will remain. If you were to calculate the benefits, it would be a thermal short beside an air pocket, vs a thermal short next to an insulated chamber. In either case, the thermal short would dominate. One inch of rigid insulation over the entire block would produce a significant improvement as it would cover those shorts as well as the cavities.

Bud

 

Thanks for both of your responses.

It would be for insulation not moisture.

I don't have a drain tile system.

This was just a curiosity issue. No plans. Shooting for passive house insulation standards, will have 2" xps outside and more inside. Just thinking about the middle.

 

I forgot to mention that the block is above ground only. At grade the block sits on a concrete wall/footing.

 

The Passive House concept is a great guide to pick and choose from, although an entire house would be a project. Deep retrofits in general will one day be the norm, at least in my opinion. All too many homes are currently being retrofitted to minimum standards that are subject to change with the costs of energy. Good luck on your planning and improvements.

Bud

 

i am going through the same issue. One of my main problems is it appears my homes cinderblocks are not ont he concrete slab but ground (dirt). I could be wrong but looking down the holes i see dirt and jagged rock sticking up in the empty spaces. this has cuased a bit of rot on some of my sills that sit on the cinderblocks themselves. I wanted seomthing to keep that moisture down inside but it looks like there is not much available. I dont have water issues in the home but i was hesitant on recovering everything up the way it was.

 

How high does the block run? I can't imagine block of any height staying put without a foundation. Usually the footer will be deeper than the thickness of the slab and depending on the type of construction might be poured separately from the slab.

 

wewantutopia -

You are right to put the insulation on the outside. This allows the walls to be a thermal mass reservoir and maintain comfort inside. This is even with the soil much warmer in the winter than the outside air.

I had a 1800 sf slab on grade lake home in northern MN with 2" XPS and brick on the outside of an 8" block wall on all sides (mainly above grade). I started using a programmable thermostat with a set back to 45F at night during the the early part of the week (M-Th). In the winter, I typically went up Friday evening to a cold structure that took a day to warm up. I decided to go with a steady setting of 65F 24/7 all week and could walk into a warmer place even at -20F on every Friday. The annual cost difference was about $50 (on LP) and well worth it because of the comfort and thermal mass inside the insulation.

Dick

 

block is a 4' above ground wall around the entire perimeter. There are like 2 corners that are like 3 inches below with minor leakage that needs to be fixed outside. I can do that part easy.

 

Kind of going off the thread here but is there a benefit of foam inside a block in that it will prevent air currents from occurring inside? I think the science is there will be both a cooler and warmer surfaces inside the block, the differential can then cause air currents, and that in turn can lead to condensation the colder surface. Then that condensate could travel through the block to the interior surface of the basement/crawl space. Put foam in the interior and no air currents = no condensation.

If I'm not over analyzing, and this can happen, then practically speaking how often does this is particular type of condensate generated moisture become a real problem?

Reason I'm asking is I've been corresponding with a company that installs foam in concrete blocks and I'd like to get my facts straight.

 

Cinder or concrete, they are both like a sponge when it comes to moisture. Air circulation within the block would result in some moisture transfer at some temperatures, but the block is already doing that anyway. As for heat transfer, block walls are about as good as a piece of plastic over a wood frame without the solar gain.

From a technical point of view, filling the blocks with foam would make an improvement, all-be-it marginal. From a cost and effort perspective, a lot of work with doubtful results. One of the worst things people do is something that produces no tangible results, thus they get discouraged and stop. One of my biggest jobs as an energy auditor is helping people sequence (prioritize) their improvements so that they will see and feel the results for their efforts. We all need positive feedback when we are spending money these days.

Bud

 

I was hoping that foam inside a concrete block could be some kind of 'magic bullet' that would take care of both minor moisture problems and provide insulation at the same time. Thought about putting rigid foam on the interior basement walls but don't know if that is advisable when there are some areas of active efflorescence on the concrete blocks. Seems like that could create entrapped moisture and we all know that is a bad thing. I've carefully read the Building Science Corporation article on basement insulation a few times and they suggest that using open cell type of rigid foam (EPS) because it can allow water vapor to pass through where the more generally used XPS rigid foam cannot.
http://www.buildingscience.com/docum...lation-systems

It would be nice to have actual reports from the field on how well EPS rigid foam boards work when put against concrete blocks which have efflorescence problems. But maybe it's a lost cause because a fire barrier (i.e. drywall) needs to be put over the rigid foam board and I'm wondering if it's just a bad idea to put up drywall with the intent that some water vapor will be passing through it.

I'm getting even more off topic now. Maybe I'll ought to turn this into a separate thread.