Hydronic floor heat vs. overhead radiant tubes 1

[humpy]

I'm looking for a very rough estimate on the installed cost of hydronic radiant floor heating vs. overhead radiant tube heaters. The space is a tractor trailer truck garage of about 9000 sf. I understand there are many variables left out but need a rough estimate to give a client. Natural gas would be the fuel. Any ideas would be appreciated. Thanks.

 

[MikeHalloran]

Just butting in...

In my limited experience, overhead heaters >never< manage to heat the floor.

The people who have to stand, kneel, sit, lie, crawl and otherwise work on that floor will worship you for getting them the floor heat.



Mike Halloran
Pembroke Pines, FL, USA

 

[atlas06]

Especially when workers are under the truck.
You application is small Square footage, I'd say go with floor. Overhead manufacturers have all kinds of disclaimers for being X No. of feet away from combustibles, etc.. they are a lot of hose reels, light fixtures hanging from the ceiling and MOST IMPORTANTLY the travelling Overhead Crane which will for sure be in the way of your overhead radiant heaters supports.

Need to watch for close coordination with plumbing, have them use a french drain style between the radiant floor bays in the facility which would lead to a sand trap (you know, they use this sand to soak in the spilled oils), warn the plumbers not to use floor drains, they will be clogged with sand.

Your 9,000 SF will cost about the same if you were to exlude the concrete assuming its a new job.

Go to

http://www.wirsbo.com,

they have some nice slab details.

Use condensing boilers, they love the cold water return (90F) temperature from radiant floors, you would be getting 94+% efficiency.

OK, may be not if you are in California, PEX tubing is not allowed there I've heard (there's been an issue between PEX tubing manufacturers and the state of California).


The other thing you can do is use combination CO/NO2 sensors to energize a heat recovery unit for ventilation instead of having the units run continuously in winter. Use radiant ehat as primary heating medium, HRU as secondary. In idea is that if teh air quality is good, no need to bring in outdoor air. And you have yourself a LEED facility.

Good luck

 

[willard3]

Overhead radiant is noisy, nasty-looking and it doesn't get the floor warm if you have anything in the space.

In-floor is quiet, it's invisible and the floor is always warm no matter what you have in the space.

Square foot cost of floor-mtd about the same as ceiling-mtd.

 

[humpy]

Thanks for the input. We don't have to sell the client on the floor heat but they wanted to know the cost comparison. I will check out those slab details. Thanks again.

 

[willard3]

EPEX and PEX tubing is too stiff for spacings recommended by manufacturers and makes tight end radii which crack.

It is sooooo stiff that it is frequently cracked by installation.

I'm with the state of CA, its lousy. There are products that are much more flexible (Onix for one) and easier to install.

 

[GMcD]

Willard3: I don't know what kind of people you've dealt with installing PEX tubing in slabs, but that comment above is misleading about the spacing. Yes, there is a limit to the bend radius of the PEX but the spacing can be as tight as you want by using overlapped end loops to get the spacing you want. I've designed and worked with Contractors to get 6" spacing with 3/4" PEX tube by using overlapped end-bends and there's never been a problem getting whatever tube spacing you need, while using wide end bends to prevent kinking. I have lots of jobsite photos and I'm pretty sure the Manufacturers' installation guides will also show how to do that.

 

[DrRTU]

What is the proposed geographic location and rough building construction details? Will the space utilize overhead crane bays?

 

[humpy]

The building will be located in climate zone 7A. This will be a metal building insulated per energy code. There will not be a crane.

 

[DrRTU]

I do a lot of car and truck dealerships in 5A on a D/B basis. I run my designs at -10 vs. yours at -20. We do more applications with low intensity IR in the overhead than hydronic slabs due to the higher first cost of the hydronic heat. I believe overhead IR has the ability to pickup the space faster than a slab. IR will warm the trucks and melt snow faster than the slab. Overhead does a very good job at keeping the floor warm. Most dealers need the floor warm to keep the floor dry. The key to the design is layout of the reflectors, tail pipe collection, lighting, oil reels and incorporation of makeup air into the design.

Independent of make-up, exhaust, tailpipe and office areas; I believe a slab design with PEX tubing, good control system and a condensing boiler will run almost 2X the cost of low intensity IR (positive pressure systems). Vacuum tube is slightly more than pressurized.

Waste oil, if available in large quantities and the need to heat an exterior slab for a wash line could help you justify the boiler.

 

[ActiveSolar05]

I would go with raidiant floor heat, PEX-A tubing. NOT
PEX-B or PEX-C... 8 inches spacing for the tubes in slab,
design a single "cooker" bay with radiant to melt off the trucks before bringing them inside. Insulate under the entire slab for your climate zone and don't be stingy... 2" thick first 4 ft from fondation edge, then 1" thick ...

 

[ontheqt]

I have to agree with DrRTU....Dont get me wrong a well designed inslab system is hard to beat for comfort and when coupled with condencing boiler will achieve nice system efficentcy. This does come at a cost!

The gas fired infrareds will heat the floors and every thing else they are "looking" at. Their design constaints need to be addressed but even with cranes we seem to make it all work out in maintenance shops, wash bays and machine shops.

A rough cost is the retail price of the infrared plus the cost of the unit to have it installed. Figure out how many u need, get a budget from ur locale supplier or rep, times two and there u go, ball park number......

Dont forget that the cost of infloor must include the up cost for the underslab insulation.

D