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heat loss and general comments on design

keyote Member Posts: 659
im doing my own system  gut renovating a 100 year town house metal studs against exterior 12 " brick structural {detached NYC NY] and 2 " closed cell foam insulation maybe another inch of open cell its expensive huh and 5/8 rock. The ceilings 5"open cell 

i made my own warm board with 12" rips of 3/4" plywood spaced 3/4" apart  over aluminum flashing 5/8" possibly 1/2" thermapex ,zones average 200' 3/4" T G solid oak finish floors.thinking triangle tube boiler.

so all of a sudden and a bit late in the game im doubting my research on 12" spacing, and cant find what i think is real world  R value for that type of wall system being un typical suburban construction

. also starting to worry pex will rub on plywood or flashing will be noisy  and weather silicone in channels is good or bad idea or if i should staple the tube into  the  jigsawed loops or if im just getting crazy

appreciate input,BTW tinknocker by trade and  fairly competent in all trades built a few houses etc.


  • Gordy
    Gordy Member Posts: 9,537
    How much

    Of this is completed?

    The wall r values will have to be done in layers of materials used.

    The flashing used under the pex, and plywood is hardly of warm board efficiency. The tubing is not wrapped by the aluminum to extract heat from the tubing, take anything circular lay it on a flat surface, and that's how much contact area your tubing is conducting heat to the aluminum, and the aluminum layer in warm board is on top of the plywood not under it. That's how warm board gets its performance on 12" centers with low water temps. Not trying to bash just help you understand you are not getting what you may think.

    As far as noise goes you may get some ticking depending on how tight the tubing is in the grooves you made, and how the returns were done, water temps used, and how the system is controlled. In other words high water temps with on off control will generate more noise than low temps with constant circulation. Water temps, and flow rates are dictated by the heat loss. Being you are using hardwood finish floor that also limits floor temps to 82* which wood floor manufactures recommend.

    12" centers verses say 8 or 6" the gain with tighter centers is lower water temps, and less stripping, not so much in the way of output to a degree. 5/8 pex verses 1/2" pex. the 5/8 gains less head, and not much more btu delivery from the 5/8 tube than the 1/2".
  • kcopp
    kcopp Member Posts: 4,259
    Not warmboard...

    but similar to Wirsbo Quiktrac. I also has a customer who did this in Gloucester mass and it did work pretty well. He used 3/8" tubing and had 8" centers on 1/2" plywood.
  • keyote
    keyote Member Posts: 659
    more info

    thanks for commenting

    Ive done the "warm board " part already, i knew it wasn't as good and I even welded a 3/4" rod to a backer plate intending to stamp the flashing into the groove but decided it wasn't worth the effort since im also spray foaming open cell to underside for acoustics to heated spaces below thought i wouldn't need the extra oomph but the flat flashing might help a bit with stripping. will go with best practices for controls though i have bought a lot of books and am sort of in the biz im still hazy on details but pretty much separate zones per room mod con boiler outside therm etc. working my way down on a four story house. this top floor will be the rental apts that pay my exorbitant mortgage.

    i know 2" of closed cell is rated at R 14  and the brick and gyp add another R3 but im pretty  sure thats a much better R16 than a 5" fiberglass batt so it seems to just use R16-17 input for the calculation wont be accurate ive read a spray foam is more like double the performance of a similar R value.batt system

     also. somewhere i read to use silicone in the channel, and thought that might help with movement and the friction on the pipe against plywood channels don't know how much to worry about friction  cutting into pipe my spaces are fairy tight except the loop ends i jigsawed are a little sloppier say 1" heavy., also wonder if using 5/8 id 3/4od  will not allow for thermal expansion in same sized square channel but 85 degrees probably doesn't expand im aware its more for friction loss than heat but figured it cant hurt. maybe i need to read more.it would be a disaster to have to rip up floors
  • keyote
    keyote Member Posts: 659

    can i make do without an uncoil er i did think a 1000' roll per floor would save a bit how bad is it pulling out 200 zone 
  • Polycarp
    Polycarp Member Posts: 135
    double-check your insulation plan

    You're inviting trouble with that insulation plan.  You have to remember how these bearing brick walls were meant to operate.  They get wet, both from liquid moisture from the exterior and vapor moisture from the interior.  They were meant to then dry to both the interior and the exterior.  Also, those walls were made with two different kinds of brick.  The brick on the outer surface is fired rather hard, but the brick on the inside is much softer.  This is because the outer bricks were meant to go through multiple freeze-thaws over the course of the winter, but the interior bricks, being warmed by the interior, were not.  The harder bricks can take that abuse, the softer ones .. not so much.

    When you add insulation to the interior, you change all that.  You decrease the drying potential to the inside, so the brick is going to stay wetter through the winter (when the water is doing the most damage).  You also make the whole wall colder, thus potentially forcing those softer bricks to go through many more freeze-thaw cycles in a year.  The net result is that if you aren't mindful of the way that you insulate bearing brick walls in colder climates, you can actually destroy them in just 10-20 years.

    You should do a WUFI analysis (http://www.ornl.gov/sci/ees/etsd/btric/wufi/tool.shtml) on the wall and see what the impact of your insulation is going to be.  Two inches of closed cell isn't a ton, and it might be ok.  But better to know than to see the soft brick in the wall start to crumble after a decade.  There are approaches to insulating brick walls to make it work right, it is worth doing some research.

    But if you decide to just go ahead and insulate it without doing the analysis, then at least make sure that the exterior of the brick wall is in good shape.  If the mortar is failing, have it properly repointed with the appropriate mortar (none of the modern, Portland cement heavy stuff) to make sure that, at least, you are limiting the amount of moisture getting in from the outside.
  • keyote
    keyote Member Posts: 659
    insulating brick walls

    Thanks for that, I have actually looked into that .It turns out in general the scientists say if you are going to insulate a solid brick wall closed cell foam is best because bricks permeable and will destroy things like fiberglass. But more to your point about the freeze thaw issue; they say several things should be considered. First the average winter temperature, one scientist put it this way dont worry at all in th south and up into new york even Boston probably ok even Toronto but north Dakota Manitoba Maine you might really be asking for trouble. this can be mitigated more than one might think by keeping the bricks dry to begin with. one article gave several strategies good maintenance of course proper coping flashing etc and even carefully researched water repellants that allow the brick to dry without soaking in more water. inspecting how the brick has handled weather so far particularly  chimney areas and above the roof-line. your link to that test inspection was also mentioned several times
  • Polycarp
    Polycarp Member Posts: 135

    If the scientist said not to worry about it up to Boston, then I wouldn't pay much attention to anything else he had to say. I've seen cases in Boston where insulation put the brick into a freeze-thaw cycle that saw much of the inner wythe turned into powder within 10 years. Bottom line, if it freezes, do a WUFI analysis.

    From a preservation standpoint, the general consensus is not to trust sealants. Though many sell themselves on keeping water out while also letting water out, none of them have been shown to really work that way. Every sealant that keeps water out keeps water in. And that is a recipe for disaster, since like you said, keeping water out of the brick as much as possible is the most important thing.

    Closed cell insulation also has its own issues. It is less water and vapor permeable, so it limits the drying potential of the brick to the interior. Even the open cell foam manufacturers with their more vapor and water permeable product don't recommend using their product directly on brick. I just went to a presentation on this a couple weeks ago; the open cell guys know what installing even open cell insulation will do with trapping moisture in the brick and don't want the liability of appearing to endorse it. There are other water and vapor permeable insulation that can be used though.

    It's unfortunate that it's not easier. Improving the envelope is generally the right thing to do, but it isn't always straight-forward.
  • Gordy
    Gordy Member Posts: 9,537

    I think we can create more issues than we resolve with high tech assemblies. Brick, and stone structures have been around for thousands of years. Technology should concentrate on making use of converting, and storing endless supplies of energy sources like wind, solar, tidal etc. rather than savoring finite resources.

    Brick, stone ,concrete, and mortars worst enemy is water, and when mixed with freezing temps this compounds it's volatility. The outsides is going to get weather like it, or not. All you can do is make sure everything is properly sealed to avoid moisture migration to the interior.

    Stone, and brick veneer assemblies on stick built homes require a 1" air space then a vapor barrier on the exterior of the studded wall assemblies to allow migrating moisture to escape through weep holes at the bottom of the wall.

    I would tend to think that you could produce the same protection on the interior face of your wall assemblies. An air space with vapor barrier, and insulation.
  • Polycarp
    Polycarp Member Posts: 135
    historic vs modern

    There's one approach that's pretty similar to what you've laid out.  You put a 1" thick mesh matrix up against the brick and then spray foam the matrix.  Then you drill holes through the brick from the exterior to the matrix.  This brings outside air into the air gap created by the mesh matrix, allowing the brick wall to dry to both sides.  It's not as good as drying to a warm interior, but it's better than a moisture trap on the interior.

    However, this is where the difference between modern and historic bricks is so important.  Modern brick veneers are made from modern bricks, hard and durable bricks with a high portland cement content.  But the bricks inside a historic brick wall are not hard.  And these walls were intended to absorb water and dry out.  Subjecting these bricks to the freeze-thaw cycle - as you do when you insulate - can pulverize them.  Controlling moisture absorption helps a lot:  no moisture freezing and thawing in the brick means no damage.  But it just may not be enough; you just may not be able to control the moisture enough to keep it out of those softer bricks.  (And seal coats aren't a viable solution.)  This is why the analysis is necessary.
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