Garage heating offer - should we take it?

HelpInAK

Newbie here. We have a new construction house in Fairbanks AK. The builder is based about 6 hours south and did not have the expertise of home building in the extreme cold climate we experience up north and this was evident in the myriad of problems we had when winter hit (nearly all other new homeowners had problems with this builder too).

One particular problem we had was the pex pipes freezing in garage slab on the far side away from thermostat and boiler. This is now the second winter this has happened and we now simply stopped using the garage for our cars (which is very hard on them keeping them outside at -40F). We were always very careful, only opening the garage for about 30 seconds to move cars, but it wasn’t enough.

We were originally advised that 55F was the minimum we should keep the thermostat. The builder is now saying that 65 is the minimum. However, since other homeowners are having freezing slab issues as well, the builder’s heating contractor is suggesting to disengage the in-floor heat and install a ceiling-hanging unit heater for the garage. The builder has agreed to split the cost of the unit an have it installed, and our total cost would come to around $.

It might be worth noting that I will only be living here for another 3 years as my job will take me somewhere else Apr 2023.

Is this a good idea and is this an offer I should take? Thank you!

dopey27177

A ceiling hung unit heater is a good idea, BUT I recommend that the unit be powered by Propane.

The propane tank needs to be above ground in a heated shed as propane will not flow in those severe temperatures.

The shed can be heated with convector base board heated by your existing water heating system.

Hopefully propane is available in your area.

Jake

HelpInAK

@dopey27177 thanks for the response. Our radiant system is propane powered with an underground tank. Fortunately we haven’t had any of the flow issues that our neighbors with above ground tanks have experienced.

On that note, our modcon boiler is oversized for the house at 199k btu, and we already run into short cycling issues from time to time. I’m not sure if that should factor in my decision making? Will introducing this heater worsen any short cycling issues?

SuperTech

I really don't like adding glycol to systems, but I can imagine it's an absolute necessity in your climate. I hope your installer is using the appropriate amount of glycol in your system and ensuring that it's air free. There's no reason that you should have a frozen slab with a properly installed and operated radiant system.
A hanging heater, hydronic or direct fired will help heat the garage, but it won't solve the issue with the radiant heating.

pecmsg

If that slab is at 55°f how is it freezing. It would take several hours of the door being open, the water will still be moving.

hot_rod

If you want a second opinion, you'd be hard pressed to find a more knowledgable cold climate contractor.
https://rockysheatingservice.com

EBEBRATT-Ed

If the system doesn't have glycol I would put in a heat exchanger and glycol the garger but there may not e enough heat in the garage

GroundUp

Did the pex burst upon freezing? We regularly see -20F in my neck of the woods and the occasional -40F, I will never install a garage radiant system without glycol for this exact reason unless it's always kept 65+. Many will argue about maintenance issues that come with glycol, but as long as the system is serviced once a decade it's never been a problem. If your lines have not burst, I would simply have the builder pay the contractor to fill the system with a 35% propylene glycol solution and be done with it. There is absolutely no excuse for freezing a radiant slab. If I were a betting man though, I'd put money on the vertical slab edges not being insulated

mattmia2

The edges not being insulated was what I thinking too, although I would go with the HX and glycol as @EBEBRATT-Ed suggested. I'm betting nothing about the boiler is really sized right, you will need to engineer the HX for water to glycol and the heat load of the slab.

mattmia2

I would also dig down and insulate the edges of the slab as I think is required by the energy code.

Hap_Hazzard

Do they salt the roads up there? Heated garages can really accelerate salt corrosion of vehicles.

mattmia2

I would think having the chunks of slush melt off and dry would slow the corrosion a bit.

Hap_Hazzard

The trouble is it doesn't have time to dry before you have to take the car out again. It just has time to melt, and then the salty water attacks any exposed metal.

GroundUp

There's often more salt on the road than snow around here lol. Yes the warmth accelerates the corrosion, but that has less to do with radiant floors than the warmth itself. Warm air temp simply melts it off and drops it to the floor so the floor and vehicle stays stays wet and salty forever. Radiant floor evaporates said moisture on both the floor and the vehicle, suspending it in the air instead of on a surface to corrode. I've had both, and have done both in the same building- radiant floor heat is considerably less corrosive to the steel inside my shop under the same circumstances

DZoro

There should be no reason that you shouldn't have proper levels of antifreeze in your system. Then hold your garage temp to whatever temp you desire. HRV can be very helpful to reduce moisture issues in the garage.
D

hot_rod

The thing with chloride sludge under you vehicle is it stays wetter longer, so it causes more corrosion compared to rock salt deicers. It gets in the fender wells and frame rails and keeps corroding.

The trucking industry claims it a billion dollar problem for the trucks, and their electronics from the sludge but also airborne mist, and then the dry dust churned up from the roads from the chlorides being used. That white dust layer is also getting into your lungs as you drive the interstates.

I know it is a lot tougher to wash that chloride residue from my truck and garage slab when it dries, you have to scrub a bit.

Minnesota and Wisconsin are the two states seeing the biggest problems with increasing chloride levels. 10,000 lakes being contaminated for example.

Whats in your water

Zman

What brand boiler do you have?
Assuming the manufacture is OK with glycol in the boiler, just glycol the whole thing and be done with it.
I don't understand the reasoning behind installing a heat exchanger.

Jellis

If the in floor radiant has not burst and can at least keep your garage warm i would just add glycol to the system and keep it as is. This would be the cheapest and easiest solution.

If it simply is not enough heat then I would install a hydronic blower unit tied into your existing boiler since you mentioned your boiler is over sized and short cycles without the garage load.

I've seen many modine hydronic heaters installed in garages here in Maine. they deliver heat much faster than radiant so will help combat the cold air when you open the garage doors.

http://www.modinehvac.com/web/products/hydronic-unit-heaters-1.htm

dopey27177

since you have propane for fuel and your boiler is oversized and short cycling you can use a a fan coil unit using the HW from the boiler to heat the garage.

Once the fan coil unit is sized properly ( large enough to heat the garage to 65 degrees as you may want to use the garage as a work shop) you can set the tstat to 40 degrees F and have a toasty space for the cars.

Additionally you also have the option of heating the space to a comfortable temperature to use the garage as a work shop.

Jake

hot_rod

Radiant floor heat is number 1 in my book for shop heat. However if you do not use the garage as a shop or stand around out there, maybe a unit heater is a better option. They ramp up quickly so you could use a setback control and save some operating cost in addition to the quick recovery.

Either a hydronic heater using the boiler, which would require glycol. Or a separate LP fired which would require a vent. Cost may work out the same.

The radiant slab could be expensive to maintain temperature if they didn't insulate to R 20 around the edges and below. Many of your energy dollars will be heating the ground around the outside.

If you do get it running g take an IR camera around the outside to see where the heat is going

Zman

@HelpInAK
Any idea how the slab is insulated? If they just used double bubble or nothing at all, that would change the plan.

Total

I have a HRV just for the garage , even when it is -30 C and a vehicle drives in covered with snow / slush ,the floor / vehicle is dry in a hr or two . I do keep the garage at 60 F .

mikeg2015

Even in Iowa, we put glycol in all
If our radiant systems. Garage or otherwise.

You never know when the home will be vacant, propane runs out, extended power outage, equipment failure, etc. unlike a traditional radiator system, you cannot drain in floor loops. Maybe blow it out with a huge air compressor line irrigation. But in the end, it’s good insurance.

sallaberry

I would glycol the system and add the propane heating unit if they couldn’t do the radiant properly I wouldn’t trust them to handle a multi temp situation. If it’s short cycling I would have the propane company make sure their delivering 11-13” anything over that will make a unit short cycle.

jumper

Heated floor is called radiant but that does not work in a garage.
Radiators above cars radiate better. The purpose of radiant is to warm you rather than the bottom of cars.

I was embarrassed when I installed heated floor in auto service garage in Toronto. And Toronto doesn't get so cold but every time door opened place was filled with cold air. Owner installed a unit heater and claimed he saved energy.

Zman

jumper said:

Heated floor is called radiant but that does not work in a garage.
Radiators above cars radiate better. The purpose of radiant is to warm you rather than the bottom of cars.

I was embarrassed when I installed heated floor in auto service garage in Toronto. And Toronto doesn't get so cold but every time door opened place was filled with cold air. Owner installed a unit heater and claimed he saved energy.

My garage would disagree with you. It is well insulated, comfortable to work in and melts the snow off the cars nicely.

Unit heaters will heat the air in the space more quickly, I seriously doubt that they are more efficient than a properly insulated slab.

Solid_Fuel_Man

I have a 2500 square foot radiant shop. 16 foot ceilings, and two 12x12 overhead doors. We drive snow covered cold large equipment in and out daily. It is set to 60 and maintains that very well. NTI trinity 110 boiler, direct pumped with ODR. DHW is just for hand washing and is done with a 1.5kw 2.5 gal electric water heater. Would do it entirely the same way again.

jumper

Solid_Fuel_Man said:

I have a 2500 square foot radiant shop. 16 foot ceilings, and two 12x12 overhead doors. We drive snow covered cold large equipment in and out daily. It is set to 60 and maintains that very well. NTI trinity 110 boiler, direct pumped with ODR. DHW is just for hand washing and is done with a 1.5kw 2.5 gal electric water heater. Would do it entirely the same way again.

That is what I expected. I figured floor heat would keep mechanics comfortable when they stood under lifted cars. Evidently not in this case.

burn_your_money

jumper said:

That is what I expected. I figured floor heat would keep mechanics comfortable when they stood under lifted cars. Evidently not in this case.

The truck shop I work in (near Kitchener) has heated floors in the new shop and forced air in the old shop. Trucks dry significantly faster in the new shop vs old and it is far more comfortable to work in. The shops are connected by a 40x20 opening so I can't comment on how opening the doors effect one system vs the other but I suspect the heated floors would be better. Unfortunately, the slab isn't able to put out enough BTUs when several hundred tons of frozen trucks pull into the shop so it will sometimes drop into the low 50s. They do have overhead water/air heat exchangers but for some reason they don't work properly.

To the OP, do you have any snow around the perimeter of the garage or has it all melted away?

Solid_Fuel_Man

Edit two 14x12 overhead doors.

Icarus

How about simply heating the vehicle... Oil pan heater, coolant heater. Then put the car in the garage and out of the wind. Oil pan heaters are a huge plus for cold climates. Modern coolant heaters can be installed to preheat the entire car through the heating system (webasto/Espar). My Sprinter Diesel van starts right up at -15f with the oil pan heater on over night, ~225 watts.

Icarus