Radiant Heat Retrofit Under Wood Flooring

2x_Tom

My mother has a small apartment over her detached garage. It's about 19' x 19'. Currently it has a 60 year old boiler in an attached shed that has most of the jacket rotted off vented into a piece of 8" x 10' asbestos waste line someone turned into a chimney, an electric water heater in an attic over the apartment with no drip pan underneath, 18' of cast iron baseboard, 2 five section Sunrads and a pump wired to run all the time in an attempt to keep the water in pipes going through the garage from freezing.

She's going to be renovating and I want to do the plumbing and heating right. I'm going to keep the attached shed, put a modcon or powervent boiler in and move the water heater to the shed, probably a 30 gallon indirect. The current radiation in the place is overkill even with no insulation in the walls. The boiler never gets above 140 or so even on the coldest days of the year. It's a wonder the condensation hasn't done more damage to the thing. I suppose that's a nod to how they used to build things.

I want to do radiant . I've done a heat loss on the place though I forget the numbers so I'll have to redo it. Keeping the floors at 80 degrees max is close to but not quite enough to heat the place once it's redone and properly insulated with new doors and windows. So the plan is the radiant will take care of the heating 99% of the time and I'll end up keeping one of the radiators or sections of baseboard to supplement the radiant when it gets down to design temp or if a tenant decides to put down a big carpet.

My question is; the hardwood floors in this apartment are about 70 years old and are in good shape. Can I put radiant heat under them and keep the floors at a max temperature of 80 degrees? Getting the radiant in isn't a problem, the garage ceiling and old insulation are going to get ripped down during the renovation so I'll have full access to the underside of the floors. I've done radiant under tile in slabs and mud jobs before but never under wood. I'm just not sure how these old floors will react to heat under them. Should I be okay if I limit the temperature to 80ish? Or am I asking to destory the flooring. Also what should the mixing valve under the wood floors be set at? I'm assuming the water temperature would be lower under the wood then in a slab.

Doug613

Hey Tom,
New here myself but I have an old Century home in Eastern Canada were we get temps down as far as - 35 C think the works out to -31F. But anyways I run radiant under the floors with a layer of SM backing it up in my house with no problems really. have not seen any difference in the condition of the floor. The construction is 1.5 in. pine and then manufactured floor on top of that (about1/2") I moved into this home about 10 years ago and the previous owner had just put it in. I find sometimes the living room can't keep up when she is real cold so I will be looking at putting a booster coil in the ductwork like a secondary heat call. I run the boiler with an outdoor sensor at temps about 130F to 140F in January, February and 110F to 120F he rest of the hating season so way under your 80ish. Hope this helps.

Doug

hot_rod

Keep the fluid supply below 130 ish. Some of that old hardwood has asphalt impregnated felt paper, not tar paper under it. Too hot and it could start to smell.

It could also have a gazillion nails sticking down, but you really want to use heat transfer plates so... An air powered die grinder is a good way to clip them tight to the floor.

Humidity is a big part of why hardwood flooring moves around, not just the flooring temperature.

ODR or constant circ is a nice way to go.

The heat load number is the important first step, find, or redo that.

of course any upgrades to the building should be first on the list, get the load number as low as possible.

Snowmelt

I'll agree with hot rod. Except for constant recirc.

Tinman

Getting the nails ground down is a job in itself. I did one in a short crawlspace recently. Not fun.

Gordy

Snowmelt said:

I'll agree with hot rod. Except for constant recirc.

Why not constant circulation? it's the way to go

Snowmelt

I guess I'm not used to it. I need more info, why is contant circ the way to go, what's the benefit of it. I know the best effient system is one that's off, would that apply for pumps too.

Gordy

Small pumps ECM. Constant circ provides even temps, and limits expansion noise. Mostly even temps. I use constant circulation for my radiant hands down better.

Gordy

For the nails think multi tool no sparks they have metal blades now. Pricey, but safe.

Second choice 4" grinder with cut off wheel those two will insure a flush cut. Die grinder yeah also. Sparks bad.

hot_rod

Snowmelt said:

I guess I'm not used to it. I need more info, why is contant circ the way to go, what's the benefit of it. I know the best effient system is one that's off, would that apply for pumps too.

Really ODR properly sized and applied is pretty much constant circ if you can take the time to dial them in.

Snowmelt

I'm going to say I need more info I that, just sounds like a waist of energy unless unless we had a solar on the circ. even then won't the gas burn? Or will it take more gas to heat the room up then the gas staying on a constant low.

hot_rod

Gordy said:

For the nails think multi tool no sparks they have metal blades now. Pricey, but safe.

Second choice 4" grinder with cut off wheel those two will insure a flush cut. Die grinder yeah also. Sparks bad.

Nails cut fairly easily. If they are those square shaped hardwood fasteners, called cleats those are really tough, closer to a concrete cut nail hardness, not sure if a blade type tool would handle that.

These grabber type screws don't saw well either This was a tile setters idea of fastening that tile cement board down. These screws some times snap with a hammer, but not always flush.

The beauty of a die grinder is the 12,000 rpm. If you use a muffler cutting, very thin, wheel that is the least metal removal and least sparks.

Air tools never get hot to the touch if it is going to be an all day grind. Ear protection is a must with pneumatic tools.

Harvey Ramer

Lets say you have an ECM circ that uses an average of 40watts over the heating season. The heating season is, say 7 months. Circ runs constantly, 24/7. At $.10 per kwh, it would cost about $20 for the whole season.

I wouldn't be fussing about that to much.

Gordy

Next choice is

hot rod said:

Gordy said:

For the nails think multi tool no sparks they have metal blades now. Pricey, but safe.

Second choice 4" grinder with cut off wheel those two will insure a flush cut. Die grinder yeah also. Sparks bad.

Nails cut fairly easily. If they are those square shaped hardwood fasteners, called cleats those are really tough, closer to a concrete cut nail hardness, not sure if a blade type tool would handle that.

These grabber type screws don't saw well either This was a tile setters idea of fastening that tile cement board down. These screws some times snap with a hammer, but not always flush.

The beauty of a die grinder is the 12,000 rpm. If you use a muffler cutting, very thin, wheel that is the least metal removal and least sparks.

Air tools never get hot to the touch if it is going to be an all day grind. Ear protection is a must with pneumatic tools.

That's ugly!

I'm thinking more like an 18, or 20 volt grinder. No cord or air hose to drag around, and get tangled up., but much heavier than a die grinder.

hot_rod

there is never the "perfect" tool for the job. Which is why we all have so many of them!

I don't do much over head work anymore.

I did end up buying all thin walled vinyl hoses for the air staplers and other air tools we used, add a couple good swivels and you barely notice them, even lighter than an electrical cords.

Gordy

Neck, and shoulders. Oh ahh.

Harvey Ramer

hot rod said:

Gordy said:

For the nails think multi tool no sparks they have metal blades now. Pricey, but safe.

Second choice 4" grinder with cut off wheel those two will insure a flush cut. Die grinder yeah also. Sparks bad.

Nails cut fairly easily. If they are those square shaped hardwood fasteners, called cleats those are really tough, closer to a concrete cut nail hardness, not sure if a blade type tool would handle that.

These grabber type screws don't saw well either This was a tile setters idea of fastening that tile cement board down. These screws some times snap with a hammer, but not always flush.

The beauty of a die grinder is the 12,000 rpm. If you use a muffler cutting, very thin, wheel that is the least metal removal and least sparks.

Air tools never get hot to the touch if it is going to be an all day grind. Ear protection is a must with pneumatic tools.

Oh my!! Bless his soul, that poor tile guy was doing a better job than most. But he really screwed the radiant! Those screws be made of hardened steel.