# HEATING GARAGE AFTER REMOVING BOILER

Discussion in 'Boiler Forum' started by Ordie, Jul 10, 2018.

1. ### OrdieMember

Joined:
Apr 28, 2018
Location:
Maine
Removing oil boiler from basement garage and installing a propane wall hung boiler in another room in basement, as per recommendations from previous threads.
Now my concern is the well water tanks and other water lines in garage, what's some ideas to keep the 21 x 25 x 8 foot area warm?
Since I'm installing propane would a propane heater be the ticket?

Joined:
Jan 14, 2009
Location:
01609
Air sealing & insulating the garage walls would be a good start, even if you're only heating it to 50F for freeze control.

Getting to the right solution always begins with a heat load calculation on that space, using leakier than average air tightness assumptions. The load at 70F indoors will be considerably higher than 50F indoors. If you want to just run an I=B=R type load calc using 50F indoors and your local 99% outdoors that should be good enough for freeze control.

Insulating the walls to even R10 (a continuous layer of 2" of reclaimed roofing polyiso is pretty cheap) would cut the heat load by way more than half, reducing the amount of radiator or other heat source needed by well over half. If using loadcalc, compare the load using "1b- Brick-no insulation" to load using "13b- Brick-R13 insulation" (A 2x4/R13 16" o.c. studwall is about the same as a continuous R9-R10.)

Just taking a WAG at it, I suspect you can get there at condensing temperature with 25-40' of cheap fin-tube baseboard operated as it's own separate heating zone without short cycling the boiler, depending which boiler and and water temperature you're running. But run the load numbers first.

4. ### OrdieMember

Joined:
Apr 28, 2018
Location:
Maine
Thanks Dana,

I don't plan on putting baseboard in the garage, looking for something in a wall mount propane unit?

Joined:
Jan 14, 2009
Location:
01609
Whatever type of heating appliance you heat it with, sizing it correctly for the load keeps it from short-cycling, and insulating the space makes a large difference in load, allowing for a smaller (usually cheaper) heating unit, and lowers the annual fuel use. Heating an uninsulated space in Maine to even 50 F is an expensive proposition.

So, run some sort of reasonable load calculation don't just guess and end up with something 5-10x oversized. Run the load calc on both the current uninsulated case, and at R10 wall insulation.

Note in central ME where the design temps are in double digits the basement/garage can be a large fraction of the total heat load if uninsulated, even if the basement/garage is only kept at 50F:

A 2x6/R19 wall at an 80F temperature difference (70F indoors, -10F outdoors) loses about 5 BTU/hr for every square foot of wall.

An 8" CMU wall at a 60F temperature difference (50F indoors, -10F outdoors) loses about 30 BTU/hr for every square foot of above-grade wall.

That's six times of the heat loss per square foot of wall you have upstairs when it's -10F outside, so it doesn't take much above grade basement/garage wall to add up to the entire wall losses of the insulated walls upstairs(!).

But an 8" CMU wall with R10 continuous insulation at the same 60F temperature difference (50F in, -10F out) only loses ~5 BTU/hr for every square foot of above grade-wall, comparable to the heat loss per square foot of the 2x6/ R19 wall at an 80F difference.

The benefits of insulated foundation walls continue below grade, but the exterior side of the foundation doesn't drop to -10F when outdoor temps do. But even at the frost depth level (more than 3' below grade most years in most of Maine) and a 50F indoor temp, 30F exterior side dirt, the uninsulated wall is losing ~10 BTU/hr per square foot, while an CMU + R10 wall is losing only about 1.7 BTU/hr per square foot.

That's heat you're paying for, whether you're thinking about it or not, and whether 50F feels warm to you or not.

If using an 80% combustion efficiency wall-thingy to heat that space it'll use 15% more propane to produce that heat than using than condensing boiler would, but that efficiency hit is small potatoes compared to insulated vs. uninsulated.