radiant heat checking on a few facts

[mlinnane]

Base
stone or sand?

What have other people used a base?
First of all I would like to talk about base. What have seen is one company does gravel, their insulation, then sand, then the concrete(and off curse the normal cement stuff). then I have seen some kinds of stone and what looks like a vapor barrior, then the steel work.

What insultaion haev people used in the floor?
Insulation what kind
Astrofoil Can not find a price
http://www.astrofoil.net/ASTROFOIL.ASTRO-WHITE.concrete.html

INSULATION-FOAM BOARDS just on the outside walls get anywhere do not need to price
Reflective Slab Insulation 12' x 50' $330
http://www.radiantmax.com/insul-tarp.html

Has anyone used the aliumium plates yet?
Also there are many radiant heat people recommend using aliumium plates they claim they increase heat transfer by 30 %. This same company advertised 1130 sq feet of tubing was over $3000 which seems high for the tubing to me when it is 37 cents a foot.

Also what type of tubing has everyone used?
I have a plumber friend and I can do some of the work myself for the radaint heat. IT does not seem that hard to lay tubing.

When doing some of the labor yourslef what has it cost you per sq foot to install radiant heat? http://www.astrofoil.net/ASTROFOIL.ASTRO-WHITE.concrete.html
please exclude the boiler cost

This is a pole barn and it is a t shape the stem of the t is 30 x 40 and then the top part of the t is 28 X 90 with a 20 foot over hang which nothing will done right now. The barn is up and we need to add the floor. I plan on having r21 in the walls and as much insultation as I can blow in the ceiling I hope to get about R44. This is going to be a boarding kennel with the kennels in the center of the top part of the t for diagram go to the following link http://207.234.238.110/kenlayout.html

What kind of tubing
Pextubing seems to be the most used. Also what size 5/8 or 1/2

 

[MikeIA]

These guys seem to be willing to work with you: Radiantec

I've only been to their web site, nothing more.

 

[keeney]

My Radiant heat setup summary:

Basement was excavated to footing grade which is 8 inches below where the bottom of the fllor slab will sit.

I back-filled with 4 inches of native dirt, compacting by driving on it with tractor (drive-in basement design). It also was rained on quite a bit before the structure was built over it.

Months later when it came time to put in the basement floor, I put 2 inches of sand over the dirt to allow ease of final leveling and compaction.

Concrete contractor came in with their compactor and pounded the sand level and tight on the top couple of inches.

Put down a vapor barrier. 4 mil poly, I think. Taped all the seams with rated tape.

Put down Owens Corning Formular 150 2" thick insulating panels. (R-10).

Stapled the tubing to the foam insulation boards using plastic barbed staples designed for this. Rented a tool to make it a stand-up job - just unroll the tubing and staple as you go.

I used Kitec brand PEX tubing which has an aluminum oxygen barrier built in. No aluminum panels needed under the concrete. It turned out to be cheaper to just use more tubing and space it 8" apart instead of the normal 12".

Poored 4" concrete slab over the top.


For my garage addition, there were a couple of slight changes:

There was a lot more back-filling of sand involved, and compacting the sand.

Skipped the vapor barrier. I taped the foam panels together instead.

I used Formular 250 insulation which is denser and rated for the load of being under a garage floor.

Instead of stapling the tubing to the foam, I layed down panels of 6x6" wire mesh and tie-wrapped the tubing to the mesh. The mesh was not used to re-inforced the concrete it just sits on the bottom. The mesh was nice in that it gave a nice reference for running the tubing in straight, even lines without having to measure and mark everything with chalk lines. The mesh worked a lot better compared to the staples. When working on top of the stapled tubing, it was easy for staples to get kicked loose as the crew was wheeling the concrete to all ends of the basement.

I used re-bar in the garage floor concrete, but this was all set after the tubing was in place. I didn;t want to tie the tubing to the rebar because I wanted it deeper - better heat spreading, and less susceptible to damage if I ever need mount anything to the foor.

- Rick

 

[woodlot]

Hi, I just finished installing radient floor heat in my pole barn, 36x45. In fact, the concrete is being poured and finished as I type this! I did not use sand or stone. I'll try to describe the process concisely: first the barn was erected and the inside graded. Then a trench was dug around the permiter of the barn from the inside. Next 24" of extruded, rigid, 2" foam (r-10) was laid in the trench and backfilled. The poles got wraped with the same foam. Next step was to lay the same 2" foam over the entire floor. After that screw-in clips were attached to the foam and 1/2" oxygen barrier pex was placed in the clips. The concrete is then poured and encases the pex, effectivly turing the entire slab into one giant radiator! I did all the work myself, just a few hours of help.

I'm hoping to start a new post on my project soon, I have lots of pics.

1/2" Barrier pex goes for about $450/1000ft. 2" extruded foam is about 23 bucks a sheet. Clips cost about 35 cents/ea. All and all about $1.55 per square ft. not counting the boiler and mechanical work (maifolds,pumps,controllers,etc.)

 

[KubotainNH]

I installed radiant heat in my 2 year old house. It's great to have warm floors. I have 4 zones, 1 for each floor and the master bedroom is seperate. The basement slab is set up as: sand base (just happens to be what the ground consists of), 2" pink 2x8' foam board (except in middle for potting affect), chicken wire anchored to foam and then the pex zip tied to the wire. Then the concrete is poured. The upper floors have the pex attached by stapling aluminum sheets to the underside, after that a reflective barrier and lastly 3" insulation. I did all the work myself with help of course. It was quite the project but worth it. I love not having registers and warm feet. I have floating hard wood floors throughout the except for the basement. I used http://www.radiantec.com/ for all the supplies and knowhow. They were very helpfull. I was able to save shipping costs by stuffing all the stuff in my Caravan. If you'd like I can post pictures of the install. The only thing I do not like is it's not instant heat.

 

[KubotainNH]

I just realized you were looking for pricing. The site gives you an approximate square foot rating I think. But with a Bock oil fired hot water heater I believe it was under 6k for the whole house. It came out to the same price as having someone install a FHA system but I had to do the labor. The slab puts off lots of heat without having plates in it but I believe it is needed for joist floors.

 

[mwood]

Wow! I never thought to add heat to a pole barn! You guys keep me thinking! When I build my pole barn, I was just going to insulate lightly and use a cheap wood stove to take the edge off so my fingers don't freeze.

Good luck!

 

[Sigarms]

A suggestion.

Call local from someone who advertises (sp?) radiant installations (as far as total price for instal).

Checked the website listed and was first impressed with pricing on the pex tubing, but... they do make up for it in the "asessories" (such as pumps and fittings).

Only thing to be aware of is the total load requirements (sp?) for the area to be heated and then figuring what heat sourse to use (the most expensive piece of the equation).

 

[KubotainNH]

The thing that would make me nervous about installing in a barn is that if for some reason the furnace kicks off and you do not know, you could end up with a bunch of bad piping although pex does expand some. You could always use an antifreeze but then would need a heat exchanger.

 

[inveresk]

Michelle, here is the typical spec. I use when I specify radiant floor heating.

Install concrete slab over damp proof membrane over sand blinding over hardcore all as normal. Over the concrete slab, lay a minimum of 3" flooring grade, board insulation. Extruded polystyrene would do ok but you can go better, phenolic foam or polyisocyanurate if you want to. The insulation has to be flooring grade though.

Staple the pipes (larger diameter is better in case of possible firring over time) to the insulation. Make sure the pipes have an oxygen diffusion barrier or you will have accelerated corrosion of pumps, valves and furnace. Some underfloor pipes kink when bent. Pipes are available that don't though. They cost a little more but are well worth the money IMO.

Place edge insulation around the entire perimeter of the floor in each room (usually 1/2" thk rolls of polystyrene 3" high). If you don't use edge insulation, you can lose a lot of heat through the edge of the slab. This can increase your heating bills substantially.

Although it's not strictly necessary, I like to overlay at this stage with wire mesh reinforcement. Some installers wire tie the pipes to the steel mesh too. The mesh mitigates against surface cracking of the concrete screed but also helps protect the pipes. A light mesh is all that is needed.

Pour a minimum 3" concrete screed over the pipes, tamping to consolidate as the work proceeds. I invariably specify semi dry, not wet. In fact it's much easier to work semi dry and, provided the mix is stored under cover, you have far longer to work it than wet concrete. Note that this type of screed is not a wearing surface. You need to finish it with carpet, timber or linoleum flooring (if you want a wearing concrete surface for a cellar, then you can finish this off with a grano topping). You have to stay off this surface for 48 hours after which it can be trafficked if protected. It'll reach green strength in about seven days but keep it protected until its time to lay the floor finish.

As a general rule, try to make sure you're designer has all the pipe circuits a similar length, maximum 100 yards. Longer circuits are more difficult for the pump to push water through so the hot water doesn't circulate as well as in short circuits unless you balance the system by choking flow rates down at the manifold. We've found this is largely unnecessary and certainly a lot simpler if you have similar lengths of pipe circuits.

It's normal that some rooms would have a very long length of pipe if it was one circuit. Break these areas up into several circuits all the same length, again no more than 100 yards. Each circuit will be connected to it's own actuator on the manifold but you can have the one room stat. control all the actuators for that room.

Choose one loop that is always on if there's a demand anywhere for heat. This is a safety device and is normally a wet zone, bathroom or toilet.

It's absolutely vital to get the design and construction right first time with underfloor heating because carrying out remedials if it doesn't work right is very disruptive and expensive. Best if you can to test the system prior to pouring the concrete. Charge the system and leave water in it while the concrete is being laid so you can tell straight away if one or more of the pipes springs a leak.

Make sure you get a drawing of the design, showing location of manifold, furnace, pumps, valves, etc. pipe circuits, heating zones, thermostats and that the design is backed up with proper calculations.

Get information on the type of thermostat. Programmable stats. are best and can give you night set back facility, frost protection if your on vacation, etc. You can also get wireless stats. which don't need hard wired.

 

[KubotainNH]

Nice post, I forgot about the moisture barrier and pressure testing the pipes.

 

[djradz]

I notice several posts discuss attaching tubing to the foam board, but make no mention of installing metal screen, mesh, or rebar. Around here, the typical installation is to use foam board, but then install metal mesh on top of. The tubing is then tied to the mesh. I personally would not install concrete without it unless I was going with fiber-crete.

 

[woodlot]

We poured fiber reinforced cement which eliminated the need for wire mesh. I know this is a debateable topic. I guess time will tell how good of a decision it was. The good thing is that I have 100% confidence in my concrete guys. They have been doing this for a long time and are known as the best around. I had to schedule my pour a few months in advance just to get these guys.

 

[inveresk]

Djradz, I always use mesh. No exceptions. The mesh has to be located within the concrete topping for it to have any structual benefit. If it sits direct on the insulation, it's only purpose can be as a grid to which to tie the pipe. These are the reasons I place the mesh over the pipe and not under.

 

[woodlot]

<font color="purple"> "The thing that would make me nervous about installing in a barn is that if for some reason the furnace kicks off and you do not know, you could end up with a bunch of bad piping although pex does expand some. You could always use an antifreeze but then would need a heat exchanger."
</font>

I will be using PE (glycol) about 40-50%. Note that this is heating grade PE and not "RV" antifreeze. There is a diffrence, also, most people do not realize that "RV" antifreeze is already diluted.

Your stament about the use of a heat exchanger does not come into play for me. I have a "closed system." I'm assuming by your comment that you have what is referred to as an "open system." That one where your potable water is also used for heating. Some people use such a system and feel its fine and safe, others refer to these sytems as "killer" systems due to the risk of legionnaires' disease. A system like that really is a good incubator for legionella bacteria. I ruled out such a system early in the planning stages. I know one big internet DIY site promotes the use of open systems. All of the "pro" sites immensely denounce them.

 

[BobReeves]

I'm wondering why they don't use copper or aluminum tubing, it would transfer the heat much better than any kind of plastic pipe. A longivity thing?

 

[woodlot]

Good question. Years and years ago (like 50) they did use copper for these systems. Now the cost and difficulty in installing have eliminated its use. One of the resources I used to impliment my system also assits people who want to upgrade these older systems with modern controlls. The cu pipe, however, stays.

After all, my barn took over 1/4 mile of pipe. Could you imagine installing that much copper? And checking for leeks? Yikes, not me! I'm pretty sure thats why radient floor heating fell to the wayside so many years ago. Now with PEX everything had changed. The system is now workable, And its simply the best heat available.

 

[inveresk]

I can see three reasons why metal pipes might be a problem. With 100 metres or so circuit length and very many bends and turns, joints would be serious weakness. With plastic the pipes are continuous under floor with junctions only at the manifold.

I expect the concrete would have a corrosive effect on the copper.

The lag time in the system is in the concrete screed rather than the pipes. Even if you could get heat into the pipes quicker, then the conductivity of the concrete would dictate how fast the room heated up and I doubt if this would be any quicker with metal pipes.

 

[Sigarms]

Your stament about the use of a heat exchanger does not come into play for me. I have a "closed system." I'm assuming by your comment that you have what is referred to as an "open system." That one where your potable water is also used for heating. Some people use such a system and feel its fine and safe, others refer to these sytems as "killer" systems due to the risk of legionnaires' disease. A system like that really is a good incubator for legionella bacteria. I ruled out such a system early in the planning stages. I know one big internet DIY site promotes the use of open systems. All of the "pro" sites immensely denounce them. )</font>

Where did you get this information?

Please list ONE CASE where an open system caused "harm".

Please list as well those "pro" sites that "denounced" open systems.

No offense, but please get your facts straight.

Your statement is absolutly ridiculous.

 

[Highbeam]

Concrete mixed with aluminum is bad news. The Al is 2+ and the limestone in the concreste is caustic and since opposites attract the aluminum steals electrons.... well, it's not good.