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Another fun problem..I have a 9×8 room, which is a passthru from the kitchen to the garage. It is a “bridge”, that is there is no foundation, the floor joists are tripled on the ends to act as beams, and they rest on the house foundation and garage foundation, spanning the 9′. This room is impossible to keep warm, as the baseboard heat in the room is tied to the house heat, which rarely kicks on as the house temp stays stable. (there is a door between the kitchen and the room, isolating it) There are R19 bats in the floor. I figure I am going to have to pour a slab underneath the room and hand dig out for footings and then some block. The ground is about 2′ below the rooms’ floor joists. Does this sound right? Is having the underside of the floor exposed this much of a problem? The architect designed it this way because my well is in the area, and I didnt want to dig for footings there. Looks like I have no choice now! Also, if I build foundation walls, basically it will be a sealed crawlspace under the room. Would this even help, or will I have to knock out some block on the house side to let air in from the house basement? Any info is appreciated.
Dave
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close it in with a curtain wall of 3/4 PT ply.. that will keep the wind out..
and change your insulation.. R19 in that situation is just not enough..
building a foundation is not going to do anything for you that the curtain wall won't do.. you need better insulation and a better heat source...
*I agree with Mike. If it's already supported at either end, why would you need footings? If you don't want to use treated ply, why not just dry stack concrete block to form a foundation wall? Quickrete makes a product expressly for this purpose. You stack your block, and then "mud" this stuff over the block. They claim it's stronger than a regular mortared block wall. I assume it'd have a stucco look to it.You could then line the inside with foam board. Technically, it'd be better to put the foam on the outside to utilize the thermal mass of the block, but it's hard to make it look good on the outside.I'd put a one piece poly vapor barrier down first. In fact I'd bring it out and stack my block on top of it. This will give a vapor tight seal and will protect the foam board from insects as well. Instead of digging a footing, I'd just stack the block right on the ground, starting with a 4" cap block, and then using a combination of 8" block, 4" block (half-highs), and patio block.Does it have R-19 because the joists are only 6" ? If not, fill the rest of the cavity with batts that fit. Then you might consider attaching foil-faced foam to the bottom of the joists. You can get it up to 2" thick and it typically has an r-value of 3 or 4 per inch of thickness. Once you stop the air infiltration, seal off the ground moisture, and add appropriate insulation, your floor should stay toasty warm.
*Why waist a single minute doing anything with a foundation??Why not address the problem here - infiltration?If the place is constructed as you say, then sheet the whole underside of the floor with PT plywood or foil faced foam. Caulk, tape, foam, whatever to make the assembly airtight. Adding more insulation in there will help.Or - have someone spray the whole mess from underneath with foam, then put up vinyl soffit material, or nothing. It will not matter because the foam will be the air barrier and the insulation.What covers the bottom of this beast now?Addressing the problem as-is will be better than screwing around with any type of foundation.What will the foundation be doing for you anywyas? Blocking wind? Yes - but so will air sealing the bottom of the floor. Will this "foundation" trap moisture? You bet, but not if you insatlla vapor barrier, etc. A lot of work for nothing!!The ideas suggested in above posts are bizarre and frightening. Air seal and insulate the floor!!Again - a classic example of architects and trades people not thinking about physics.I would have never in a miilion years let a client or architect build a space like that without proper air sealing and insulation. No foundation here is a blessing, really.-Rob
*Hi Dave,What's the flooring construction?Tighten that room up, top and bottom. It shouldn't be hard. If your FG is just hanging between the joists underneath with no air barrier of any sort, that makes the FG nearly worthless. Cover it with ply or foamboard, or if you are so inclined, pull the fg out, sheath the bottom and blow full of cellulose.But another major problem is the room has no heat in it to start with. Insulation will only retain heat, not create it. Is the existing baseboard hydronic or electric? If it's electric I would just put it on its own thermostat. If hydronic, I would probably just supplement with a small electric baseboard w/thermostat rather than go to the trouble of upsizing the hydronic unit, which may still not do the trick if the zone that it's on never kicks in anyway.Crusty: The last thing you want to do in an area that is subject to freezing is stack a block wall right on the ground that touches the room. The gound will heave with the frost and lift the block and push the room all out of whack. That is why foundations have to be dug below the frost line in the first place.Steve
*hey rob....what's this ? ((The ideas suggested in above posts are bizarre and frightening.)))kinda harsh... but then what would i no ? i'm just bizarre...
*well, its not quite as bad a setup right now, lol..Im not a total fool, though I can act like it..I left out some details, I didnt want my original post to be a novel. Anyway, the floor joists are 2x8, I put in R19 because that was shown on the drawings. I put 1/2" cdx against the bottom of the joists, and sealed it with spray foam. There is 5' of hydronic baseboard in the room, but because it is tied into the house's first floor, which is insulated well and doesnt drop below the thermostat setting often, it is rarely on. The room loses heat faster than the main house. There is R19 in the walls, and R30 in the ceiling. 2 entry doors and a window, all are new and decent units. The first winter with this room the room was chilly, I assumed it was because of the floor being cold. Over the summer I put studded PT walls sheathed with 1/2" ply under the end beams, which act like the wind curtains suggested above. I even sealed around them with spray foam. Well, after the first few nights of colder weather this year, the curtains did not help. The room still seems to lose heat faster than I believe it should, and again I just assumed the floor was the problem because the floor is cold. (armstong stick on tiles over 2 layers plywood subfloor, I did this before I learned how to do tile). Ok so now if the floor is not the problem, and I dont find any major air leaks, whats next? Only other thing I could think of is the fact that there is no slab poured under the room, and I was wondering if the cold ground was giving off the cold to the floor? But then I guess a slab would also get cold, doing the same thing. I will double check for air leaks, and if none Im ready to try something to take care of this..thanks again,Dave
*drptop.. one of the problems is you have four of teh possible 6 sides exposed to the ambient temp.the curtain wall , sealed, will reduce this to 3 of 6..so , if your design temp. is zero.. a curtain wall will mean the design temp under the floor will be say ... 20..so instead of a delta-T of 70... you will have reduced it to 50..then the insulation has to make up the rest of it..calculate a heat loss for each surface and you may find the problem....sounds like you have used a lot of fiberglass (walls , floor, etc)..it is easy to NOT achieve the design R-values with Fiberglass... a few gaps here and there .. and you can reduce it by half.....
*Well, you're right about the frost heave. I never think of that because I live in the temperent south and I have NEVER in my 43 years seen a case of frost heave. We have to watch this regional stuff!Rob, as Mike points out, if you do a curtain wall right, assuming you seal and insulate the floor properly, you absolutely WILL have a warmer floor. As Mike states, heat transfer is directly related to the difference in temperatures. A properly sealed and insultated crawlspace becomes a "thermal buffer" between the living space and the ambient air. It will be warmed somewhat by the floor, further reducing the available delta T.As for frightening, how could anyone who claims to understand physics think you'd be better off with the freezing wind whistling under your floor (even if it is properly insulated). Have you gotten so caught up in "radiant" that you've forgotten about convection? Radiant may the the main heat gain problem, but convection is by far the dominant heat loss problem.
*Infiltration...main problem and out-flitration!...Sort of related to convection but not!near the steam, cause it's chilly here!aj
*So I will replace the r19 floor insulation with r30, and keep my stud wall "wind curtains". Do you think I should pour a slab over the ground thats under the room? I am just wondering if the ground is giving off a lot of the cold, since the wind curtains are in place and the floor is still cold. Dave
*How bout a diff zone in this room. It's cool because the heats not on. Seems the room would hold it if it had it. Either that or leave the door from the house open.
*no... if you have a curtain wall...you shouldn't put a slab over the ground....there is a delta -T in the ground also..go down about 6 feet and the ground temp is apx.. 45so, the heat is moving out of the ground from the 45 deg. zone to the surface ((the 0 - 10 deg. zone...))))the slab won't keep cold out.. it will actually keep heat out if anything..the curtain wall.. and increase the insulation....
*Crusty - regarding the crawl as thermal buffer - won't the value of this thermal buffer be directly related to how warm it is and if it;s any warmer than the exterior temp, isn't that only due to the heat (the owner is paying for) escaping? I think even Fred L comes down on your side on this - but that is based on insulating the crwal instead of the floor and the surface area of the crawl wall being less than the floor ares. In think with this small area that Rob is correct.
*bill.... if you do a standard heat loss calc.. one of the entries is for wind scour...ie: a coastal or mountain home should use a wind-loss factor.. a well protected home could use static loss calcs..but all heat loss is calc'd for worst case, standard conditions..this is the same thing as ((wind-chill)) factor..and the earth is a constant radiator.. until you get far enough north to perma-frost.. so it can alsway be included..ground source heat pumps utilize this constant heat movement...the heat from below, moving to the cold surface , warms the heat- xcahnger tubes buried in the trenches....in an 8x9 crawl space .. some of these things become very marginal//but the problem of trying to heat this is basically because it's just as he described.. it's a ((bridge)))...
*Mike sort of said it, but nothing "gives off cold." Heat always moves from hot to cold. Actually "cold" can only be defined as the absence of heat.Bill, in my first reply, insulating the foundation walls was a key factor. The idea is that once heat gets into the crawlspace -- wherever it comes from -- it will remain there, to an extent, depending on the temperatures of the surrounding surfaces. And yes, some of the heat comes from the house floor. It will never come to full equilibrium -- you will always be losing heat from the crawlspace, but if properly insulated the delta-T available to the floor will be less than if you let the wind howl under your house.Of course, it all starts with a properly insulated floor (as Rob says) sufficiently tight to stop infiltration/exfiltration (as a.j. says). But a well executed crawlspace WILL give you a warmer floor.I have a new house built on a crawlspace. I am not insulating the floor this winter, at least not at first. I will be sealing off the vents in the crawlspace. If the floor is unpleasantly cold, I will insulate and I will start with one of the two back bedrooms, neither of which has any southern exposure and both of which have the same amount of western exposure. I will be able to measure the effects of insulating vs. not insulating. Should be interesting. Depending on what I find, I may just insulate the foundation walls and not worry about the floor.
*It seems to me that if you did the heat loss calcs (I didn't) you would find that five feet of baseboard is not nearly enough, especially with the thermostat in another area (of different design). The room has high exposure, minimal insulation, two doors and a window. Air seal, add more baseboard or other supplemental heat, add foam where you can and blow cels.Good Luck,Jerry
*All good info, but just to add to the discussion about the ground and a slab and/or footings. We can get frost up to 3' deep, code here is 42" for footings. So the ground is definately freezing in the winter, so I would assume the ground under the room is also freezing. This is why I figured the ground was the source of the cold, because the wind curtains are very air tight. So if I dug down for footings, did block walls slightly above ground level and then built conventional stud walls as the air curtains, the ground under the room would be isolated from the frozen ground outside the walls. Then I figured the ground under the room would not freeze, and not be as cold. I also thought that putting down a vapor barrier and slab would prevent moisture from the ground damaging anything after everything would be so air tight under the room. Is this not true? There used to be another door in the room, leading to the back porch, which is now gone and the back porch is framed in and part of my kitchen project. Since the door is gone,I can get another 5' of baseboard in, and I will do that also. But am I wrong in thinking I should isolate the frozen ground under the room?
*I would put radiant heat in this room way before I added the foudation and I would make sure the bottom is sealed well for infiltraition...And put it on it's own thermostat...A zone of baseboard or better radiant floor would be well received...near the stream,aj
*Dave,If you are intent on digging, I wouldn't bother with the block foundation, since you don't need it structurally. If the diggin is easy and you are just trying to reduce the heat loss from the the ground under the crawl into the exterior grade, why not just bury a slab of foam insulation on edge for your "foundation", then run your curtain wall down to that (and continue the foam up the back side of the curtain wall).I'm sure Gene L will pipe up about insects and foam, and I don't know much about that. Maybe Gene can advise as to the best product to use or whether this approach is complete lunacy and would lead to bugs in your rugs.Steve
*Believe me, Id rather not dig, I just want to warm up this room. It would be almost impossible to give this room its own hydronic zone, just because of the problems of getting feed lines into the room. I am planning on redoing the floor in tile, and could sink one of those electric mesh heating pads in the thinset. Im paranoid about electric heating items, always worried about them starting a fire. That may be my only option on getting heat on its own zone though. I hope they dont use electricity like electric baseboard, I have heard many horror stories of sky high elecric bills. Thanks again,Dave
*The original post was asking about constructing walls to act as a wind screen. I said they are bizarre and frightening for two reasons:1 - There was a post that mentioned dry stacking block. How much wind is this going to stop?2 - Constructing a foundation wall in situ is one big pain in the butt versus swinging around a few sheets of foam.As his later post confirms - stopping the wind washing didn't do squat.I realize that lowering the temperature differnece accross the floor will help, but this is based on the same level of insulation. Mt point is that 2.7" sheets of polyiso foam weigh 6 pounds each. This room needs 3 sheets - 18 pounds and $70 will now add a real R-20 to the floor. You guys care to debate the wind effects blowing accross 2.7" R20 sealed joints foam?Constructing a PROPER crawl space which would still be unconditioned will take much more time and money. Concrete prices by us have doubled in the past three years. Slab mix is now going for $93 per yard. You need less than a yard, so would you pay the half load charge or bag mix? Bag mixing sounds like alot of fun here.You guys are discussing frost walls. So you go down 4' and up say 2'. Two walls 9x6 - 54 square feet each that need to be insulated in order to have heat gain from below. So you now have to insulate 128 square feet to lower the temperature some unknown degree.After hearing this was a DIY glass job, I will second the above notion to blow this in with cels.I am not "stuck on radiant heat transfer" either. Radiant is that last thing I was concerened with here. Though tell me this, how would cold "come up from the ground" without radiant.Have you given anythought to where the heat is going from this room? What is overhead? Is this room also DIY glass? Side stapled flanges?I may do the math on this one - I am slow this week (for now anywyas).-Rob
*I did the math.Used Fourier's Law - simplified for comparisons of same area.Q=delta T/RQ is Heat transfer rateI said 10 dgrees outside and 70 inside.I said add R20 to the floor for $70. I'll assume the floor is currently R15 which seems doubtful.Q=60/35 = 1.714 (the units do not matter here)Now, this R20 will yield the same results as increasing the temperature of the space underneath.To find an equivalent temperature difference to the R20 we do the following:Again, Q=delta T/R. To get the same heat transfer rate we uses the 1.714 number from above.1.714 = delta T/15delta T = 25.71 degreesthis means the crawlspace would have to be 44.29 degrees to yield the same effective heat transfer as adding R20 to the floor.Whether or not the unheated, insulated walls of the crawl space will allow enough geothermal heat gain to maintain 44 degrees is more complex that I care to do.I forgot to mention that you will have to insulate the garage end of the crawl as well - another 64 square feet. Which now brings the total to 192 square feet of rigid insulation for your crawl.Infiltration may not be that big a factor here. With the insulation only partially filling the space, and perhaps not touching the air barrier the batts are essentially useless.If you think you can construct a crawlspace, and maintain it at 44 degrees without heating it for less than $70 than go for it. I have lots of work you can do around here you obviously have plenty of free time 8-).Remember - if you connect this new space to the basement via a hole in the wall, then it becomes a heat load and ongoing cost as well.-RobP.S. - I reread the whole thread. Sorry for my ranting on my first post, it was early and I was quite stunned at the idea of using any type of concrete or masonry to make the space more comfortable.
*drptop70ss,Correct me if I am wrong but it sounds like you don't have much heat getting INTO this room in the first place. Having 5 feet or 50 feet of baseboard in this room won't matter if the baseboard does not even get energized. Put this room on it's own zone of heat (as per AJ) and be done with it.Phil
*I will put the room on its own zone. The only reason I thought I needed a foundation, is because I built the room and did insulation the same as the rest of the house. R19 walls, R30 ceiling, R19 floor. I can leave the door open to the room, get it at 65 degrees same as the rest of the house, then close the door. While the rest of the house stays warm and holds the heat without the temp falling much over time, that room will cool off much more. The only difference is lack of a foundation and the floor was cold, so I figured that was the problem. I didnt mean for this to get into a shouting match. I am a DIY, but by no means average, I did everything in my house from excavation up so I am not your average home depot shopper trying to figure out how to replace an outlet. But hey I am always learning, and thats why I ask questions. Not because I have nothing better to do, I want to do stuff right the first time. My architect speced the room to be built this way, so I did, how was I to know it wasnt a good design?
*You refer to R19 and R30 and so on. If you have used fg batts, the real value is probably much less. These values are based on laboratory tests with tolerances of the framing in the thousandths if not ten thousandths - assembled very carefully by people in white lab coats. You may have been as careful and precise - I haven't seen it - but I have my doubts.Plus, what Rob suggests is easy and quick and not expensive - try it for a year and see if it isn't sufficient - plus add a little heat in the room and make sure it is reasonably sealed and perhaps insulated at the ceiling.
*Rob, how could you ask, "Though tell me this, how would cold "come up from the ground" without radiant."You KNOW that cold doesn't "come up" -- heat always flows from hot to cold, whether by radiation, convection, or conduction.I don't think you can ignore radiation in this case. It stands to reason that if radiation is the dominant cause of heat gain in your attic where the delta-T is 50 degrees (130F roof - 80F wall), then it's going to be a significant heat loss in this case where the delta-T is even higher at 60 degrees (70-10, your example).The floor absolutely will radiate heat directly to the frozen ground (no conduction or convection needed). Since radiation varies as the 4th power of temperature, raising the ground temperature to 44F as you said, will cut the radiation loss in half. No one said NOT to insulate the floor. I'd use 2" foil faced foam with the seams taped as you said. But I'd also get rid of the wind which absolutely causes at least some forced convection, and I'd raise the crawl space temperature if possible to reduce the radiation losses. And yea, I'd blow cells in the attic.But if you put one of those small (8" square) ceramic heaters in the room (has it's own thermostat), it will stay toasty warm (assuming you've added the required insulation). They are amazingly thermally efficient.
*You just lost a bunch of credibility Crusty...ceramic heaters are incredibly efficient?...Like more efficient then what other electric heating device?near the stream, liking your radiance but not the ceramic crap,aj
*OK, a.j., "They are amazingly thermally efficient." is an off-the-cuff statement with no data to support it. Perhaps it's not true. By my experience with these is that they will heat a small room very quickly. We've used one as our only source of heat in a bathroom for three years now (we're in a rent house at present) and it doesn't seem to be expensive to run. The thermostat works well (on the one we have) and it will keep a room quite comfortable. When we drag it out this year, I'll get my amp meter and infrared thermometer and do some testing to see just how much energy it takes to heat the room.
*Right...Well if ya get more energy out than is inputted...apply for patents quick!....They are convenient but a toaster has the same efficiency within a wee bit as does even a light bulb...and with the light bulb ya can read FineHomebuilding whiie on the can...Keep up the radiance thread though!aj the rascal
*Droptop,I'd much rather discuss your car than this room. But here's what I've got to say about it.1. Get off the whole thing about the foundation. Rob was right, and why waste time and money on that?2. Your "architect" needs to find another job.3. Duh, the room's cold. It's got 2 doors and a window to keep it that way. It needs HEAT.Sorry to be blunt, but you've gotten some good advice. It seems pretty simple to me!Now, let's talk about that ragtop...MD
*OK, so here is my plan based on what you guys have given me. I am going to add 2" of foil faced poly insulation to the bottom of the floor. Now, should I strip off the plywood that sheaths the bottom of the floor joists first, or just add the poly over the plywood? I still am not sure whether I should keep the wind curtains or not, I understand now that the heat will move to cold. If I get the floor insulated well enough, I shouldnt need them, correct? I am also going to add more baseboard; if this isnt enough I will put this room on its own zone somehow. Hey mad dog, Ill talk musclecars anytime, if you are into chevelles, check out Team Chevelle (www.chevelles.com)Thanks guysDave
*Chevelles. Awesome. Nothing like the Chevys of that era, love 'em. Sorry to be a pill, I think you're getting the right idea.I'll have to backtrack through some of this thread, I can't remember what your floor is now, top to bottom. I'll wait a few minutes, see it you pop in to tell me!
*Dave,I was in danger of becoming a motorhead in my youth, but thought better of it. I did have a fun 69 AMX for a few years. I still think it's one of the most nicely proportioned cars ever designed. Of course it's not in a league with say a Jaguar XKE. I also have a real weak spot for 59 Corvettes. But my tastes are pretty idiosychratic. I still want to own a Gremlin before I die.Leave the plywood there. Just tack up the foam and be done with it.Steve
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Another fun problem..I have a 9x8 room, which is a passthru from the kitchen to the garage. It is a "bridge", that is there is no foundation, the floor joists are tripled on the ends to act as beams, and they rest on the house foundation and garage foundation, spanning the 9'. This room is impossible to keep warm, as the baseboard heat in the room is tied to the house heat, which rarely kicks on as the house temp stays stable. (there is a door between the kitchen and the room, isolating it) There are R19 bats in the floor. I figure I am going to have to pour a slab underneath the room and hand dig out for footings and then some block. The ground is about 2' below the rooms' floor joists. Does this sound right? Is having the underside of the floor exposed this much of a problem? The architect designed it this way because my well is in the area, and I didnt want to dig for footings there. Looks like I have no choice now! Also, if I build foundation walls, basically it will be a sealed crawlspace under the room. Would this even help, or will I have to knock out some block on the house side to let air in from the house basement? Any info is appreciated.
Dave