Radiant for a workshop .. slab depth ?

ScottMP

We will be installing radiant for a 30X60 workshop and garage for a construction shop.

My question is a few years ago, I went to a Wirsbo seminiar where they talked about not insulating under the floor to allow the earth to heat up and allow the doors to be open and closed without loosing to much heat.

Would like some opinions on this.

How about insulating and making the slab depth deeper by digging deeper and then putting insultarp, about 8" soil and then pouring the slab.

Or am I over thinking this ?

Garage doors will be opened and closed alot during the winter, for plowing and sanding.

Scott

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=237&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"</A>

Mark Wolff

Wirsbo HePex Install

The Wirsbo rep apparently gave some misinformation. The ground will not store the heat as he assumed. The heat will be sucked out of the concrete at an amazing rate, just about doubling your heat load. Twice the boiler will be needed to keep up.

The best current building methods include 2" blueboard under the slab and 2" blueboard around the perimeter, to keep the heat from migrating out from the slab and footer.

Typically 4" slabs work ok for garages, but with the equipment it sounds like you'll have, go with a 6" slab, even consider fiberglass mesh mixed in the concrete (gives a slightly rough finish, but increases the strength greatly.

As for using an insultarp with dirt above, concrete is a much better heat mass than dirt as you know. Here in AK we have no problems with 6" slabs and blueboard not keeping the shops nice and toasty even with frequent door openings. If you want a little fudge factor, bring your spacing in a couple of inches between tubes and the recovery will be quicker.

ScottMP

The way I remember

was edge insulation and then slab insulation on the border, leaving the center open.

Scott

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"

Bill Nye

Pay me now

or pay me later. Do the insulation, the building is not so big that insulation would cost too much. The planet Earth is a mighty big heat sink.

Scott, I heard the perimeter insulation preaching in the past too but I think the sermon has been changed. A contrator I worked with specializes in concrete. He puts his vapor barrier and insulation below a layer of processed gravel because he says the concrete cures harder if the water is not trapped by the poly sheet.

We've done a few projects together but I never paid enough attention to the concrete part. He adds plasticisers and elastisemers and whatever to the concrete.

Ask your guy if they are going to bolt equipment to the floor. Like tire machine or hydraulic press or stuff that has to be anchored to the floor. Keep your tubing deep or out of the area.

My friends shop is 120x60 or bigger. The tubing is installed and he will be using a Black Gold waste oil boiler or something when he gets to it.

steve gates

I'd insulate and thicken the slab. Done thick as 12".

The thicker slab will hold and release heat much better.

On the 12" slab we did the boilers went down on low pressure once and we didn't lose 2deg. in the four days I was at one of Dans April seminars.

Keith Hotaling

I would

definitely insulate with 2" foam under the entire floor and the edges. When I contacted Wirsbo about a similiar design, Elaine Hoffman there told me that the thicker the pour the slower the response. It will still work, just that it will take longer to heat up and longer to cool down.

John Felciano

Concrete

As I understand it with concrete the longer it takes to dry the stronger it is.I'm sure there are some exceptions for very thick pours, like the Hover damn.I've seen concrete guys go around and poke holes in the poly so it sets up faster.Usually because they don't want to wait long to get their trowel machine on it and finish.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"

hr

With barriers under

a concrete pour, all the "waters of convience" have to leave through the top of the slab. This will generally lenghten the time before the finishers can put the final finish on it.

That's why they go around and poke holes in the InsulTarp or 6 mil!

A better way is to have the batch plant add water reducing agents. Calicum is commonly used around here, but it can really quicken the "set" time and may get finishers in trouble on large pours, if they are not careful with the amounts..

Also calcium increases the potential for corrosion of the rebar or remesh. Calcium also created problems on the old copper tube installed on rebar or mesh jobs!

Concrete should be mixed with just enough water to consolidate the mix. A typical yard of concrete would be 1800 lb aggreate, 1400 sand, 500 cement and 30 gallons of water. Finishers commonly like to add water to allow easier flowing of the mud. Adding water also increases the potential of those small hairline shrinkage cracks, often seen the next morning

Every gallon of water added, reduces the psi rating of the mix by 200!

Some trivia about concrete, the most consumed product

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"

Joh n Brickey

According to the Wirsbo computer design there is no differance between 1" and 2" foam under the slab. Just use 1" and save the money. I have found that if you use sand under the foam instead of gravel it won't crack as bad when you walk on it. Insulate the perimeter as well alot of heat is lost out of the side walls. We just did a job the homeowner put foam board all the way around the outside of the building,laying flat. His choice not mine.