How much difference will insulation make?

[Sneeze357]

I have a little 10x10 room in my shop where I keep my tools. I keep it at 50 degrees with a 1500w electric heater and use a dehumidifier. In the summer I will have A/C. The 2x4 walls are insulated with R11 fiberglass. I went crazy with a can of foam and some caulk and sealed the whole thing up like a refrigerator. The ceiling is not yet insulated.

Just to see how much power this uses, I left a kill-a-watt meter hooked up for 24 hours. It was around 40 degrees in the shop. Left the thermostat set at 50. It used almost 5 kilowatts in that time. That is too much.

Of course, I need to insulate the ceiling. I will use 9" R30 fiberglass. I'm wondering if it would be worth the trouble to add more insulation to the walls? R11 is not that great. I could easily add another 3.5" layer of insulation inside. (I still need to put plywood on the walls) Or maybe some rigid foam?

If I'm using 5 kilowatts to keep it at 50 degrees now, just how much could I cut that down with more insulation?

 

[3v0]

Heat rises so focus on putting as much insulation as you can in your ceiling. With no insulation in the ceiling you have no effective insulation.

With enough insulation you can heat it with a light bulb or three.

 

[volleyball]

Fill cavity with fiberglass and then put foil faced foam board over it under the plywood. You cannot have the foam exposed inside.

 

[Scott H in Wheaton]

What you have now is like a styrofoam cooler with no lid on it.
Is the floor insulated?

Not only does heat rise, but it also moves towards cold. So you could have heat loss above AND below.

 

[buddyboy]

warm air rises, heat moves toward cold.

all your warm air is going to the ceiling and then the heat from your warm air moves thru the ceiling to the cold.

insulate your ceiling

when you calculate your energy use again, make sure you do it on a day that is simular in temp.

if you're not happy and if your slab isn't insulated then that would be your next step... foam on top of slab and plywood flooring on top of that

good luck

 

[GarageWrench]

I didn't see it mentioned, but where are you located?

I added r-30 to the ceiling of my attached 600 Sq-ft garage after I installed my heater. So far this year I have only used the heater a few times. The insulation helped more than I had imagined it would. One exterior wall isn't even insulated. I'm in the PNW so it doesn't get terribly cold but its been nice going out to a warm garage.

If I were you I would add the R-30 in the ceiling and go from there

 

[volleyball]

Tough to justify the loss through a 10 x 10 floor. If you add anything, you raise the floor and then you have threshold issues. Unless it is dirt.
Without knowing location, we are hindered in offering relevant info.

 

[Falcon67]

My 12x24 work area runs around 66 with the G73 on "dot 2" below LO. It cycles 2-3 times per hour. The walls are R13 and the ceiling is R13 right now. the seams are caulked to prevent air leaks, which is a key item. The 48" "door" is a king size quilt. Very little power required to keep it nice.

 

[bczygan]

Welcome to GJ!

Where are you located?

You need DOUBLE the proposed R19 in the ceiling. You need R38 minimum. Make the top layer of batts un-faced.

 

[rburke65]

You won't need any insulation in your climate!

 

[JakeKohl]

Your measurement of energy use also included the extra energy to bring the room up to temperature so may be a little higher than what it takes to maintain that temperature.

Also...in a heat mode, most of your heat loss will be through the ceiling. Additionally, if you are using an electric heater that doesn't move any significant air, the hottest air will be right on the ceiling (heat rises) where the transfer of heat will be even faster with the higher temps there.

If you insulate the ceiling significantly, I bet your energy use will be almost 50% of what it is now.

 

[Highbeam]

I have an insulated mechanical room, 5x10, in my unheated shop. In this room I have water treatment systems and plumbing so I need it warmed above freezing as well. I filled all the wall cavities with insulation and the slab beneath it is insulated though connected to the shop slab so conduction keeps the slab the same temp as the main shop.

I covered all walls with OSB and caulked all seems. See, it's not just insulation but air sealing to keep the heated air in the room that I find most important. The door to this interior mechanical room is an insulated, weatherstripped, exterior, metal door, with a threshold. You want to keep the heated air in the little room.

Of course insulate the ceiling. But R-11 in the walls to try and maintain a 10 degree temp differential is plenty. Going from R-11 to R-19 is not going to get you much. Going from R-0 to R-30 is huge.

Shut the door and leave it shut as much as possible. Opening a door to a small room like that quickly lets all the heat out and you start over.

Leave the kill-a-watt on there for a week to log data and give you a much better representation of consumption.

 

[theoldwizard1]

Heat rises so focus on putting as much insulation as you can in your ceiling. With no insulation in the ceiling you have no effective insulation.

With enough insulation you can heat it with a light bulb or three.

You want as much insulation in the ceiling as you possibly can get. If there is any way to criss-cross 2 12" batts, do it ! Like the man said, with a room that small and well insulated you could likely heat it with some 100 watt incandescent light bulbs !

 

[Milton Shaw]

The 5 kwh most of that could have been to get the room up to temp and not much of that spent to keep it at temp. Insulate the ceiling and then read it every day for a week. I think you will be amazed at what the reading is after a couple of days just maintaining the temp.