Foam on retrofit 2-wythe brick mass walls?
Hi, i live in Baltimore. I am thinking of adding insulation to my 2 story + basement house. It was built in 1938. It has a double layer of brick for external wall support (total 8 inches). This is not veneer cladding but a mass wall, supporting the roof. I think originally there may have been plaster applied to the brick on the inside. However, the walls sound hollow when I knock on them, and someone has suggested the house may have been retrofitted in the past with perhaps some furring and a layer of drywall. In the unfinished basement, this brick is exposed. When I power washed the house 9 years ago when I moved in to remove the ivy, which covered the whole front of the house, I could see water in the basement draining down the inside brick face from above. So it appears to function as a drainage space.
Now, I am thinking of using RetroFoam, which could be poured in without expanding, to fill that space for insulation. I would combine this with finishing the basement. But I am concerned about what I have been reading from building science dot com about the effect of insulation on the brick, in making it colder and thus more prone to staying wet. Since this is 2 wythes thick, my concern is greater. The Retrofoam dealer will be coming out to see my house soon, but has told me over the phone that with these old houses they need to assume that there can be no drainage to the inside, after so many layers of paint and who knows maybe even a vinyl wallpaper for all we know. Nevertheless, they have not seen a problem to the masonry. I think the thought is that there is enough drainage to the outside or even down the foam. It is 60% closed cell foam with the remainder being some sort of resin. It is not a vapor barrier but vapor retardant. What would be your recommendation?
I realize now that my experience with the power washing likely means that the brick needs to be repointed. Should this be done at the same time as foam, to cut down on the rain seepage? Or are they useful for now as a drying pathway?
For the future, I can imagine the brick may need an external cladding with furring strips, (perhaps foam) and stucco. Should I perhaps be doing this now instead?
Thanks in advance for any and all replies.
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If you're thinking of eventually insulating and re-cladding the exterior, then you would be better off going that route from the start. Not only will that eliminate the leakage problem and need for repointing, but it would retain the considerable thermal mass benefit of the brick by keeping it within the conditioned space. And, of course, there would be no issue of freeze-thaw damage to the brick structural wall.
Robert. Thanks so much for the response. I was just reading in Building Science about how foam is a good retrofit answer (though from just a few years experience with it). But what you say about the thermal mass is really interesting and gives me pause. I am indeed interested in the thermal mass to help control overheating from a new south-facing sunroom addition I am planning. I gather if I put foam on the inside of the brick, I will be removing it from acting as thermal storage. By the way, I neglected to say that this is only about 1 inch of space I am talking about, so the need for external insulation is looking stronger. I just have to convince my wife...
You can't use a south-facing exterior brick wall for direct thermal gain for a passive-solar house unless you abandon the idea of insulation. (If the brick wall were thick enough, and if you lived in the perfect climate like the U.S. Southwest, such a scheme might work -- but not as well as an insulated wall.)
Once you wrap your head around the idea that an insulated wall is better than an uninsulated wall, then Robert is right -- exterior insulation makes more sense from a thermal performance perspective. You won't get any direct thermal gain on your brick wall, but it will act as a thermal mass.
For historic preservation reasons, most people want to preserve their brick exterior. But if you're willing to live in a stucco house, then by all means install exterior rigid foam and call up the stucco or EIFS contractor.
Let me try that formatting again...
Actually, this has been done at least since 1881 when Edward Morse patented what, in 1964, became known as the Trombe Wall (popularized by French engineer Felix Trombe). All it takes is a simple pane of exterior glass and a small air space, because glass is transparent to visible light but far less so to infra-red radiation (heat).
Since the outer collector surface is radiantly decoupled from the exterior air, the absorbed solar energy moves through the thermal mass by conduction at a rate of approximately 1 inch per hour, allowing the energy to be released to the interior environment in the evening.
Of course you're right about Trombe walls, although getting approval for a full-height Trombe wall on a historic urban brick building might be difficult.
Then there's the problems of performance -- uninsulated Trombe walls are rarely if ever the best solution if you're hoping to upgrade a building's thermal performance.
Take a look at Tripolymer Injection Foam info and dealer links at http://www.InjectionFoam.com
It has an Rvaule of 5.1 per inch and it's made from phenolic resin same thing billard balls are made from.
Phenolic foams have a history of problems, including shrinkage, water absorption and metal corrosion. It's possible that the newer varieties have overcome some of these, but there is as yet no data on which to base a conclusion.
Thanks to all.
Martin - Yes, I wasn't thinking of direct solar gain, but of thermal mass within the structure of the house. Heat coming in the windows would be stored in the brick. This brings up another question. For the sake of simplicity, I hadn't mentioned that I am planning an addition off the southern end. A 15ft x15ft family room would have at the far southern end a 3ft x 10ft bay window area jutting out, with basically floor to 8ft ceiling windows on 3 sides. There is an adjoining sunroom planned to the east coming off the south wall of the kitchen, 10ft by 10ft, basically all windows with a shingled roof. This is chosen for the sake of utility and aesthetics, but I like to think I can incorporate this into soem passive solar gain. I am sensitive to what I read about overheating. The southern exposure would be about 70% glazed, though as a percentage of total house floor space, I think all the southern glazing holds to the about 8% I read about. My question to you is then about the fact that by building an addition, I will be encasing a double brick wall down the middle of my home (the original south wall). This wall is uninsulated. It has drywall or plaster (not sure) on one only side. The sunlight coming in It is contiguous with the external walls and the concrete basement. The sun streaming in 18 ft away from the bay might hit the wall, but I doubt it, so I doubt much direct thermal gain. But as a mass, I hope this 15 ft double brick wall could store some heat. Thoughts? I am thinking of putting drywall on this wall - would this affect things much?
On Retrofoam and Tripolymer Injection Foam, I gather from web surfing that these are phenolics utilizing formaldehyde. All the manufacturer and dealer websites seem to have the exact same wording, and the clear effort is made to distance themselves from the older urea-formaldehyde and dancing around the issue that they are a new generation of phenolic-formaldehyde except with lower formaldehyde concentrations (they do note that in burning there is minimal "aldehyde" vapor detected). I read there is a class action suit in Canada against Retrofoam because its actual formulation and chemical family became apparent (the websites tend to call it "propietary") and formaldehyde is still prohibited there. It's all very murky. Even on our Department of Energy website, it lists the various foamed-in-place insulating products with a category for phenolics and then "some less common types" which include "tripolymer foam" - as if it were a different type. My feeling is that Robert is right - this new generation of formaldehyde resins may be safe for humans (and biodegradable and safe for the environment as claimed), but the general murkiness and less-than-forthright presentation, it's hard to see the data on which to feel confident. I'll have to ask the dealers for more information.
With that much south glazing, you're going to get overheating even if the mass wall was all direct gain. In fact, at winter solstice noon in Baltimore, the sun will penetrate almost 14' through a 96" tall window - not nearly far enough for your brick wall to serve as direct gain.
To maximize the amount of heat absorbed by the mass wall, do not cover with drywall but keep the texture and rich color of the wall exposed and use a highly reflective flooring - such as urethaned light-colored wood - to move the solar energy to the wall.
I would also incorporate a way to vent the sunspace to the outside.
That sounds like the type of solid advice that I need. I've been thinking that perhaps what I need is someone who knows solar design to look over my plans. My architect is very good at making it fit in with the historical neighborhood, but I don't think he's trained in knowing the engineering repercussions in terms of heating and cooling. Im certainly not, which is why I've been spending time on this site and Building Science. Do you know how I might find a solar consultant to look things over and give advice? Just like you've done, except I would pay for his or her time for an in depth recommendation. It also ties in with my desire to bring in central cooling, which will require ductwork that I don't yet have. And since I will have new ductwork for central cooling, and will need to heat the addition, the question then arises whether it might not be better to switch my oil-furnace to radiator heating to geothermal, which would combine heating and cooling...and give efficient use of electric power, which could then potentially be covered by some solar panels. I just got a price quote that 4 solar KW would cost $29K but after the federal 30% and further state tax credit, and after selling my clean energy credits to the grid (to fulfill utility requirement for their quota of clean energy), this falls to $12K. But an HVAC consultant I just met tells me if it were his house, he would keep the wonderful radiators, which is something "all the new houses in the country don't have." He tells me, "You'll never get as comfortable a heat as you are getting right now." So perhaps I should go with extending the radiator system and using ducts for isolated AC cooling.
You'd probably be best served by someone local to you who could look at your existing house, evaluate the solar access at the site and analyze your plans.
But if you'd like whatever feedback I can offer from a distance and can send me pictures of the site, the existing building and the view to the south as well as current floor plans and plans and elevations for the additions, I do consulting for a modest fee.
You can contact me at HouseWright at Ponds-Edge dot net.
Thanks, Robert. I think I'll take you up on that. I saw from a website on "natural building" that you have special interest not only in passive solar but other structural building issues. I also have many questions along those lines, so I'd appreciate your ideas on many fronts.
I'm going to start a new question on the use of plywood vs. OSB. It's something I'll also be asking you but would like others to chime in on. Of course, you can also tell me your thoughts on this forum.