I am planning my new dream woodworking shop and am interested in opinions from others regarding insulating a wood framed floor. I am planning a 20×52 ft shop with standard 2×6 walls, truss roof and a framed wood floor ( probably 2×10) floor covered with T&G decking. I will be heating with an oil direct vent space heater and fans to move air around the open space. I will be building the shop completely by myself with the exception of the concrete delivery. The location is Kimberley BC Canada.
For frost protection I am planning a perimeter concrete strip footing about 3.5 ft below grade with the polystyrene forms that you fill with concrete extending out of the ground about 1 ft. Down the center of the foundation I will have a series of concrete pier footings to support a treated wood laminated beam that the floor joists will bear on.
My question is regarding insulating the floor. I am considering 2 options:
1) Since the concrete/polystyrene walls are insulated already, option 1 would be to just insulated the rim joist all the way around the perimeter and not put any insulation in the actual floor. I would put a poly vapour barrier down on the soil beneath the concrete footings.
2) The other option is to just insulate the floor between the joists. This seems to me to be negating the insulation benefit of the styro insulation on the concrete wall?
One person I talked to recommended circulating warm air down under the floor to warm it, and to minimize moisture buildup. It seems to me that you would lose a lot of heat to the ground.
I am interested in any opinions/experiences you all have regarding framing and insulating a wood floor. I am in the planning stages so I am not set in any way as to how to build the floor or the foundation, just want it to be energy efficient and straightforward to build by myself. Thanks everyone,
Lyall in Kimberley
Replies
Lyall ,
I would think the building would be better insulated from the temp changes if you insulate the floor and the ceiling and walls.
my shop is 28 X 45 drywalled and insulated except the floor , the guy who built it before we bought it was saving dollars .
You might want to ask this over at the Breaktime folder as these folks are more into construction and full of wisdom .
regards dusty
We either insulate the walls and maybe the ground and then put some (not much) heat in the crawl space to keep things from getting icky (mold and such) OR we insulate the floor and vent the crawl space to keep things from getting icky.
If you insulate the walls, and then do not provide any ventilation in the crawl either into the main space (heated space) or to the outside, then you are asking for all kinds of long term problems.
Doug M
I'm going to suggest from a little different direction. I'm not sure of your terrain or your annual rainfall in the BC area but if you have moisture anything like we do in West Virginia, I would make sure you make provision to drain it away or be sure your insulation is sufficiently above the moisture and their is adequate ventilation between the shop and the moisture. I ran into a spring where I dug the footing. It was low enough that I put to drainage pipes around the foundation with plenty of gravel and so far the basement is bone dry. If some kinds of insulation becomes wet, it is absolutely worthless.
I have a 24 x 32 wood framed shop with a concrete foundation, ranging from 2' above the footings, to 4' above the footings, insulated inside the crawlspace, against the concrete, with 2" of rigid foam, along with the rim joist, about R-14. Floor is 3/4" plywood over 4X6 timbers, no insulation. The 2x6 walls are insulated at R-19 to R-23 (north wall), and the attic (15' high ceiling) is pour in at R-38. The place isn't tight yet, but is not hard to heat with a small wood stove, and doesn't freeze at night, even without heat. This is in eastern oregon where over night lows in single digits are not unusual. The floor is never cold, and the only circulation is a box fan hanging from the ceiling, which I only use occasionally. I have occasionally considered a ceiling mount radiant gas heater, for those times I have a project that needs to meet a schedule in the middle of winter. The earth, below frost level, maintains pretty close to 50 degrees, so you only need to heat from that temp, if it is in your insulated space, and you can keep the heat in. Insulate, and insulate some more.
This will not address your question but would be of concern to me: You mention a "truss roof" installation.
Be sure you have enough (?) room under the bottom chord of the trusses to swing long materials.I think there are truss designs where the bottom chord has an arch to it.
Frosty
"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
Some people will disagree with the following, but they ARE WRONG.
Essentially you will be building over a shallow crawl space.
MAKE SURE the crawl space is SEALED and there is NO VENTS.OLD school vented crawl spaces and it was PROVED to be wrong some 8-10 years ago.I built a 3000 sq ft house on a site with a shallow water table that didnt allow for a basement.
USED 4 foot insulated concrete wall panels after raising the site about 20".THE KEY IS - KEEP the MOISTURE DOWN and into the ground.
After walls are set:
INSTALL a PLASTIC VAPOR BARRIER and pour a skim coat of concrete over it.
THE 44" basement (crawlspace) remains DRY & COOL with little temperature variation year round.BUILD the rest of the building and insulate that well.
You may want to install a pull up set of steps because once the building is finished, the crawl space will vary less than 10 degrees year round and REMAIN DRY. Obviously the site requires proper contouring and drainage must be addressed if of any signifcant issue.I will try tomorrow to dig up the crawl space literature about NOT VENTING THEM.
THE KEY IS - KEEP the MOISTURE DOWN and into the ground.After walls are set:INSTALL a PLASTIC VAPOR BARRIER and pour a skim coat of concrete over it.THE 44" basement (crawlspace) remains DRY & COOL with little temperature variation year round.
I'm hoping your right as I did basically the same thing.
We are expanding our livingroom and the new space is essentially a crawl space. In one end of the space there was an opening and the wind would blow right through it making this room a virtual wind tunnel. It's an old house.
What I did was install 2 layers of 2" styrofoam between the floor joists (2" x 8") and 6 mil poly under the floor joists. On the ground I installed 40 mil plastic - recycled from the landfill. Probably should have skim coated with concrete but $$$ said otherwise. Was toying with the idea of gunite instead of concrete though. Oh well....
On top of the 4" of stiff styrofoam I added R-19 faced fibreglass batts stapled to the top of the floor joists, topped off with ¾" T&G plywood.
End of wind tunnel!
Regards,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
a substitute for the concrete would be some 1b stone.
The key element is making sure the PLASTIC vapor barrier is TIGHT to the edges, the seems are over lapped and taped, no HOLES, and it remains that way.
The JOIST package needs to be air tight with ZERO penetrations.The reason for the skim coat of concrete is for people USING the shallow space for storage. This allows for movement and placement of objects without any chance of vapor barrier penetration.ANYBODY building a new addition/structure/house that doesnt make SITE prep #1 PRIORITY AND controlling moisture under the LOWEST LEVEL,
well, lets just say they should only be allowed to be day workers.THERE is absolutely no reason for any MOISTURE in a crawl space or basement........................if the MOISTURE cant be controlled,
the SITE is UNSUITABLE for building.Kidder, you WILL have NO problem if the vapor barrier remains intact.
Keep a close IIIII out for burrowing vermin!
You have reasonably low electric rates, so I would do a 5-inch concrete slab, with 12-mm reinforcing bars at 300-mm on center both ways, over 4 or 6-inches of foam, on grade, with resistive electric heat wires built into it.
Don't know your area very well but I can imagine it gets cold. My first question is, Is 3.5 feet deep enough to get below the frost line? If it isn't, the foundation is subject to heaving. Check with your neighbors. If there is a problem with moisture in your area, I would use film on the outside of the foundation. It is wonderful and will keep a basement bone dry. Don't neglect the other suggestions of putting poly on the floor either and if you can, put a drain with plenty of gravel around the footing to drain any free water off. It wouldn't hurt to insulate the floor but with all your other insulation I'm not so sure how much heat it would save.
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