I'm building a bungalow just north of Vancouver BC.

I'm planning to install a radiant staple-up system using joist-trak panels installed between the i-joists (19" centers).

The majority of the house is supported on piers, so the crawl space under the floor system is open to the air and gets very good circulation.

I think I understand from reading this forum that a good way to insulate will be to install unfaced high density fiberglass (eg R30C) between the joists and snugged up against the pex/plates. Hopefully I can find some cut to the 19.2" width! Is this still an acceptable solution?

Do I need any kind of air / vapor barrier?

I'm also wondering what to cover the underside of the insulation with - we have a normal population of mice but also some river otters who have been happy to spend the winter in a neighbors insulation and I like to keep them all out! I've had suggestions ranging from chicken wire to plywood.

Thanks,

John

This is place for solid foam boards or spray foam. You will not keep vermin out of fiberglass without steel.

The key to insulating radiant sub-floors is to make them airtight. Cut the insulation to fit and caulk it in. Exterior grade plywood would be my choice and watch out for those pesky otters!

With JoistTrak in place depending on how deep the I-joists are you may be able to do it with plywood/OSB and a blown-fiber fill (cellulose is cheap & effective in my neighborhood). Since the floor will be elevated in temp above what other floors are you want to go something like 1.25-2x higher in R than what you would over ventilated crawlspaces elsewhere. Foam would work but it can get out of hand price-wise.

Ply or OSB can be made into a decent air & critter-barrier. The borate fire retardents in cellulose insulation are eye-irritants to mammals, and toxic to ants & termites. Critters won't normally nest in it even if they get in. If the I-joists are deep enough to be in the right range when fully filled with low-density cellulose, that'll typically be cheaper than a minimum-R of open cell foam (which is cheaper than closed cell per unit-R), and will be nearly as air-tight.

In the moderate maritime climate of north-Van you don't need an interior side vapor barrier, but if the inspectors insist you could staple up some poly snugged up under the JoistTrak & Pex, and fill the void between the poly & sheathing with low-density cellulose (not "dense-pack", which would stretch the poly too much.) You definitely want to avoid exterior-side vapor barriers though.

Thanks for the quick replies!

I failed to mention that there's no road access to the new place. Everything has to be taken by boat, if it fits, or by barge if it's big. So there's no inexpensive way to get a truck with blowing or spraying equipment onsite.

Would high density fiberglass work as well as foam or cellulose? I know I can get bales of fiberglass in the boat!

John

High density fiberglass batts allows much lower air flow than low-density goods, but it will ALWAYS leave gaps & voids (particularly in I-joists where you have to cut it to fit.)

Rental cellulose blowers from box stores aren't super-heavy or bulky (one strong guy, or two pencil-necked engineers could wrestle the most-common box-store rental Force-I blower onto a boat: http://www.inteccorp.com/Force1.htm ) and dry-blow cellulose comes in easily stackable 12-15kg bales.

To do this job with blown cellulose you'd need to install the plywood first, and to make it a good air-barrier it's best to lay a beads of caulk or construction adhesive along the joists, (at least at the seams), then paint 5cm either side of the seams with a decent acrylic-latex caulk to form a bonding surface for housewrap tape.

In each joist bay starting about 1m from one end, use a hole saw to drill a series of holes every 3-4m that are just a bit larger than the hose of the blower, so that it can be directed in at an angle. Stuff rags in the holes to loosely block them to avoid too much dust & blow-by, then start at one end blowing first toward the end until you hear the blower stalling then toward the next hole. Keep blowing until it stalls, then move to the next hole, blow back toward the first hole, etc working your way along the joist bay. (You'll definitely want goggles and a quality dust mask for this.) It's useful to have a rag wrapped around the hose at the entry point too (some use a cut-off sleeve of an old sweatshirt), to limit the blow-back in your face. When you're done, use construction adhesive to seal & re-install the hole-saw plugs (or cut a bunch of squares to cover the holes, and glue & screw them in an air-tight manner.) Done in this manner the density will be high enough to restrict lateral air movement within the fiber layer, and it will fill every nook, crevice & void, eliminating thermal bypasses above the fiber layer. (In 20-30 years it may settle enough to have a 5mm air gap between the sub-floor and the fiber in the lower density parts, but it won't be a big enough performance hit to measure easily, and would still outperform a batt-job's day-one performance, even before the mouse nests got going.)

That's what I'll do then!

Thanks for taking the time to provide such a detailed answer.

John

I hope that you have not wasted your money on the insulation yet..... The best way to insulate your crawlspace is to get rid of all your foundation vents! I recommend tearing them out and replacing them with a cinder block, This will definitely keep the mice and otters out! ( there is no need for vents in a crawlspace! check your building codes and this will verify that I am correct, the only people that recommend placing insulation in your floor joists are insulation dealers and people that have not researched the topic correctly no offense) After your close your crawlspace vents i recommend placing 2" closed cell rigid foam board along the inside perimeter of your foundation walls. After you complete that I recommend that you encapsulate your crawlspace with a heavy duty vapor barrier at least 12 mil thick (6 mil is garbage and will tear as soon as you step on it) If your foundation walls are properly insulated and your crawlspace is encapsulated properly it will be a mini basement so to speak, and then you will be able to open a heat duct into your crawlspace allowing you to warm your floors through the crawlspace, For a very informative website on this topic go to crawlspaceinfo.com It saved me a lot of money and mistakes, it definitely worth looking at.

For the life of me, I can't understand why anyone would want to increase their duct leakage/heat loss area from a 12" diameter pipe area which can be run in conditioned space to a basement sized area that borders cold dirt over hundreds, if not thousands of square feet.

Well, I s'pose if he put about 10" of rigid foam on crawlspace floor and put up a continuous perimeter wall around the foundation piers (also with 10" of rigid foam) to make it a fully enclosed space then foam-sealed it he'd be at about the same heat loss, but the the floor temp to the toes wouldn't be as friendly and the cost of the wall & insulation considerably more than a dry-blown cellulose between the joists & joist-trak approach.

Methinks Derek1980 has a different mental picture of the foundation, and not a clue about soil temps vs. air temps in Vancouver, or how to make radiant floors work.

The notion of using an overheated crawl space to provide radiant heat to the first floor is simply gonzo. The heat transfer of crawlspace air to the wood sub-floor is so much LESS efficient than joist-trak the crawlspace air temps would have to be downright TORRID to make it work, even with an air-tight and well-insulated crawl space (ergo the need for much higher R walls & floor.)

No credit for fierce independence in the face of industry standards or basic thermal dynamics? You guys are a hard bunch to please.

I think Dana has no idea about what she is talking about!! First of all it is absolutely ridiculous to place rigid 10" rigid foam on the floor of a crawlspace! and 10 " on the walls is also a over kill to say the least!! There is no need to insulate the columns you just have to wrap them correctly with a vapor barrier and properly secure it the vapor barrier on the crawlspace. I have only encapsulated about 300 crawlspaces in Michigan, Ohio, and Indiana and have instructed hundreds more from all 50 states with this method and have nothing but positive results, just go to crawlspaceinfo.com all the information is there to verify my claims. Dana1 make sure you do you research before talking bad about some ones suggestions it just makes you seem even more ignorant!!

so why would you do all that, and add to your heat load, when you can just use a closed cell foam on the floor joists directly and protect them from moisture that way?

Because the crawlspace is part of your house, If you treat it like a basement , seal your vents and encapsulate it correctly your heating bill will go down because you are no longer letting cold air into your houses envelope. People do not realize how much cold air and humidity they let into they're houses by having open crawlspaces. This will also prevent pipes from freezing, prevent your floor joists from forming mold and potentially rotting which will weaken the homes integrity. Like I said please visit the link that i posted and read through it and I am sure you will understand why i strongly encourage everyone to use this method!

Derek is correct about sealing the crawl space, but I would leave the rest to others.

...because you will have cold floors. Insulating the floors from basements and crawl spaces doesn't necessarily make them warmer. In fact the cold air coming off windows will chill a floor better if a relatively warm basement or crawl space is isolated by foam.

I have taken a lot of insulation down from crawl spaces and insulated the parameter, laid 6 ply for a vapor barrier and opened conditioned basement to the crawl space...much warmer floor. Naturally if the floor will be radiated the insulation goes up and the crawl space is rightfully forgotten, but should be closed to the outdoors and open to the basement if possible.

My only objection is the use of air for heating...now that is primitive. heehehee

Yah Dana, what planet are you from ?...hehheheheheheheheheeehehehee

Oh gosh, leaking ehehehee

Hey Derek, you are new here, you might check Dana's previous posts.

Dana was kidding and not a girl, hehehee

Posted By Derek1980 on 18 Mar 2011 04:50 PM
I think Dana has no idea about what she is talking about!! First of all it is absolutely ridiculous to place rigid 10" rigid foam on the floor of a crawlspace! and 10 " on the walls is also a over kill to say the least!! There is no need to insulate the columns you just have to wrap them correctly with a vapor barrier and properly secure it the vapor barrier on the crawlspace. I have only encapsulated about 300 crawlspaces in Michigan, Ohio, and Indiana and have instructed hundreds more from all 50 states with this method and have nothing but positive results, just go to crawlspaceinfo.com all the information is there to verify my claims. Dana1 make sure you do you research before talking bad about some ones suggestions it just makes you seem even more ignorant!!

My ignorance underwhelms me in the face of your omnicience, Derek. ;-)

Since you'd have to run the crawlspace at about 110F or more to achieve the same heat flux through the floor as with joist-trak bolted to the sub floor you've multilplied the delta-T between the crawl and the average winter air exterior in Vancouver several fold, and as well as between the crawlspace the subsoil, so you have to go way more than double on R-value to achieve the same total heat loss as R30-R40 under the joist trak. (Without knowing the specs on the rest of the house it's difficult to say with certainty if it truly need to be 10", it might only be 6", or it could be a foot.  But it sure isn't zero, or 2". 

I'm all for conditioned crawlspaces & insulated foundations, (I'm truly sold on the concept and then some) but hot air ducted into a crawl space to provide radiant heat just doesn't cut it.  Can't cheat the physics- it's a crappy way to provide radiant heat to a floor.

Since this is an open air pier foundation, with no existing perimeter wall mentioned, (truly open-air on piers, if the owner/poster is to be believed) so you'd have to build something structural first,onto which to hang the insulation. You can't just stuff some cinder-blocks in between the lattice work and pronounce it "good"- there isn't a structural wall to start with. Whether it would be worth the trouble to do that rather than going R30-ish or better under the radiant floor and making it air-tight between the insulation and crawl as suggested, is a dubious proposition at best.

I suppose it's OK to promote your business in a low key way, but this particular crawlspace and heating system is perhaps the WORST example of where that might be of use.  Here it's neither more effective nor lower cost.  Sealing up with OSB under the joists and dry blowing it full of cellulose is infinitely easier than building & insulating a full perimeter crawlspace wall around it to make a conditioned crawlspace.

Badger was right. Damned RIGHT I'm kidding! (And last time I checked I hadn't undergone the gender-transformation thing, but that's not relevant here.) 

This is reductio-ad-absurdum, to point out that you'd obviously overlooked two salient points: 

1: Low open air pier foundations aren't the sort of "crawlspaces" worth conditioning (since there are no walls with vents to brick up, as you had suggested).

2: Even if it did have walls, since they're heating with a hydronic radiant floor (not hot air) using better-quality heat-transfer plates, to achieve the same cushy floor temps by ducting hot air into the crawl space blows up the rest of the design requirements to ludicrous proportions (like 10" of foam).

I'm sure there will be ample opportunities to sell the virtues of conditioned crawlspaces- you just managed to pick crummy example to start with.

Oh ouch...glad I'm not in the woodshed! heeheehehee

Man, and I thought I got it here some times.....
I do like the concept of closing up the vents and 12 mill plastic on a traditional foundation. Perhaps on this fellows project given location a perimeter of pressure treated 1/2 ply would be a good addition, but agree, high density insulation is easy.
How to cut to 19 inch wide, a good razor knife, lots of fresh blades and a long metal straight edge..... you'll be stuff-in itchy in no time
Best to all this week end
Dan