Radiant UNDER existing 6" concrete slab

Sepp

Hi All...

I will start off saying that thanks to the help from here (and some other sites) I was able to maintain and manage the steam system in a 100 year old brown stone for 20 years. The system was balanced, quiet and very warm...

Move forward to our current project... Restoration of a 1930's factory building with a 1970's addition.
The 1930's part of the building is heated with steam radiators converted to hot water.
Other than some maintenance, it seems to be working well.

However, the 1970's building was a disaster. We think it was originally heated by the gas fired dryer in the printing press that was in the building, but subsequent owners updated to hot water and radiators... But the building was so poorly maintained, that the bottom of the boiler was rusted/rotted out and after the pipes froze, they installed a forced hot air 'blower' (can be seen the photos).

The space will be converted to a residential space and we are trying to do the least amount of build out, keeping the raw industrial feel... Not cover it up with finishes.... The goal is to have it look pretty much like the photos.
We will be replacing the crappy vinyl replacement windows with casements.

The main space is a large room (30'x 50') with 18' foot ceilings.
>will have kitchen & bathroom with shower & main living space
The floors are a combination of 6" concrete slab & plywood subfloor.

The full basement is completely below grade (12 feet at some points).
>will have workout room & movie room & storage. Perhaps a 'bonus room'...
It maintains 55° pretty much year around.

The partial 2nd floor also has concrete poured over corrugated metal frames.
> will be bedroom & bathroom & closet

There is also a huge un-insulated skylight (10' wide x 28 feet long).

The goal is to just polish the existing concrete floors. We have considered flooring materials but because of existing stairs we would rather not change the elevations. We also really like the look of the polished concrete.
The wood fill-in area is yet to be determined.

Are we crazy to think we could put radiant UNDER the existing slab and generate anything worth while?
I've been told the floor could provide about 60% of the heat needed, but we'd need to augment it with something to 'heat the air' as well. (Floor could provide upto 25 BTU/sq.ft., but the space needs 35 BTU/sq.ft.)
I know that this would be very slow to respond. And based on what I've read here, perhaps I mis-understand that the floor wouldn't necessarily be warm to walk on?

We have also considered radiant panels on the ceiling for the area covered by the 2nd floor, which (I hope) could provide heat to the first floor and also heat the 2nd floor slab... (It's hard to understand... see the photos).

I have tried to do some research and we do have an engineer involved. I'm just trying to see if our ideas have any merit before I fight for them.

Other info: The walls are concrete block, 8 to 12" thick. Roof has 1.5" of insulation.
Yes we need to improve some of this... But the skylight is probably the main heat loss at the moment.

Thanks,
S

Jamie Hall

On the skylight. Can you double glaze it? I'm envisioning adding an inner set of clear glass panels (leave the outer roof side alone). You could even triple glaze it. That would help a lot. Plain glass will do.

It's a real shame about the old steam system. Steam puts out a good deal more heat than hydronic does, for a given radiator. Also doesn't freeze... however, it is what it is.

I would at least consider radiant panels overhead in the main space, particularly under the mezzanine.

hot_rod

The concrete slab is suspended on metal span decking? You would fasten tube to the bottom of the metal somehow?

kcopp

For me I cant imagine the system ever responding as a staple up from underneath. You may be better off cutting in grooves from the top and doing a thin pour over the top.

Zman

I don't see many windows. Are you going to be required to provide some mechanical ventilation?
I tried to push through that much material once. We got past "cold floors", not sure anyone felt that they were warm. That home had forced air as a supplemental.
If you have a typical "W" pan on the bottom, would you be able get full contact with the heat plates?
This one might be a better candidate for panel radiators, although when you put them on the ceiling you lose the convective heat and are relying on radiant. Our local school has some mounted about 15' up in an entry. I don't notice any heat at that height. Might have to bring the IR cam next time..

Gordy

What will be finish floor? As is?

I'm with @kcopp pushing radiant from underneath would be a battle with 6" on concrete. The insulation needed would also have adverse effects to the rooms below for the industrial esthetics you wish to maintain with the pan decking.

I'd do grooves in the concrete. Concrete staining can have some fabulous results for the industrial look you wish to keep.

hot_rod

If you want an industrial look and feel maybe a modulating CoRayVac. It would have no problem heating the floor with those tall ceilings.

http://www.robertsgordon.com/infrared-applications


A small boiler with panel rads up stairs and in the basement.

What about cooling?

Gordy

Those would be the ticket. Especially with the high ceiling, and skylights. You can experience the warmth this time of year at most big box stores.

Zman

hot rod said:

If you want an industrial look and feel maybe a modulating CoRayVac. It would have no problem heating the floor with those tall ceilings.

http://www.robertsgordon.com/infrared-applications

I guess if you get them positioned just right they would do the job. They are pretty intense. When you stand right under one you think it will melt your hair. When you move a few feet, you are cold. I see lot's of them in the cold outdoors or at ice rinks.

hot_rod

It looks like the modulating versions may be less of a head burner? Like any heating appliance if sized to the job and application they should be a nice fit for a high ceiling space.

The museum application would be an example of the need for a comfortable space below the heaters.

When you are tall you notice the intensity of the mushroom style radiant heaters at outdoor dining locations

Sepp

Thank you so much for the feedback.
Not what I wanted to hear though ;(

Re: Grooving the floor: Would probably be way too destructive to the look, even with stain (which we have done in other areas), it would be impossible to match the aggregate and changes the desired look beyond what we would like.

Re Infrared: I know the infrared heaters you are talking about - see them Home depot all the time... Probably not what we are thinking of look wise... And the noise would be a bit distracting.
Aesthetically we want to keep the main volume empty and clean.
(think gallery space)

We'd love to A/C.... BUT not sure we can afford the upfront capital at this point. We are looking at 'mini-split' units for the 2nd floor spaces. The engineer is working up something that we could bid... He thinks it's at least 7 tons, which will probably be way out of our budget, but maybe we can phase it for a couple of years in the future if we design it right. (We are putting new A/C & ventilation in the front parts/work spaces of the building).

As far as ventilation, we are looking at an erv, but the skylight has huge vents that draw the hot air out in the summer.
We might be able to combine the fresh air intake with the oversize kitchen exhaust (we are hoping to have an oversize kitchen range)... (*YES we plan on entertaining quite a bit, thankfully except on the hottest days the room is very comfortable).

I'd really love to find someone who could help us use the inherent thermal sink of the basement into the energy program of the space, but it would take the exact right person who has the experience and know how. *Hint Hint....
The basement stays cool all summer.
We also have good breezes and I'm hopeful that if we put a 'attic fan' in one of the skylight vents we can force even more nighttime cooling air thru the main space. (since the bedroom will be it's own zone it should be ok.)

It's a complicated problem to solve, converting a space that was never intended to be used this way into a residence. Especially since it was purpose built for a printing press with HUGE ovens.
(there is a 2.5" gas main to the space....)

We are in the planning phases of a solar install, although we wouldn't get enough to cover the cost to use electric heat....

i COULD go on and on about this building... we really are in love with it... It's a gem... (I should have attached photos of the exterior in the first post - Before & after of the front



attached)...

Thanks again for all the guidance.
I'm sure I'll be following up, once we move further into the designs.

Zman

This project reminds me a bit of a local project where they turned a 100 year old school into library/community center with lots of offices and meeting rooms. The used Runtal panel radiators under the windows and entrys. They did the code required ventilation with exposed spiral ducts and ERV's.
The project came out really nice.
I am having trouble getting my head around 7 tons of cooling.
If you had the ducts in place you could add some AC later if needed.

hot_rod

Be sure you perform a careful heat load. Maybe a blower door test also.
Block walls, un-insulated?
Single pane skylights
1.5" on the roof
You have a lot of problem areas.

Gordy

With the history of this buildings purpose. Heating was not a problem with the equipment used. Probably cooling more so in the day.

I love what your going to do with it!