Need Insulation Advice For New Shop

[Kyle241]

I'm planning on blown-in cellulose for my walls (24x32). Not certain what I am doing with the ceiling yet though as it may end up being a combination of some sort.

 

[forgeblast]

I would think about critter nests, the spray in will keep the mice etc out, while the fg batts give them a great place to live.

 

[Gary Fowler]

I dont like blown in insulation as it settles too much. In a year, you will have a void at the top. I have 6" bat in my house with 15" of blown in fiberglass on top when new and it is less than 12 after 1 1/2 years. I prefer the fiberglass batts or foam. I used the 6" R-19 bats in my shop in walls and ceiling with insulated garage doors and a 1500 watt heater will keep it as warm as you like. I have one in it now on low heat (750 watt) and with 25F outside this morning it is nice and warm inside and the heater thermostat had it cut off. I also have the reflective insulated boards under the galvalume roofing which helps keep it cooler in summer. I have it sealed in the ceiling(9' 8" height) and walls with 3/8' plywood inside and 1/2" exterior grade plywood outside so there is some insulating value to the wood compared to sheet metal siding or vinyl. Attached photo of shop with currently under construction 14 x 30 addition for boat/ lawnmower storage. I dont plan to insulate this portion right away, maybe later if it starts getting too hot in summer.

 

[wedge40]

No one asked but I will. What will the insulated area be used for and how do you plan on heating it? These two things will help decide how well to insulate.
My self I'm using radiant floor heat, spray foam and fiber glass on the walls, then fiberglass in the ceiling.

Wedge

 

[monteu]

It will be a metalworking shop. A place for a couple lathes. I am thinking I will use a radiant tube heater to heat it. I really don't need to keep it over 60 degrees. I guess I a little confused by my options. I can go fiberglass or spend 4x as much polyiso board or 7x as much for spray foam. The rollout fiberglass insulation that you put on between the purlins and sheet metal is so much more economical than anything else. Appreciate all the thougts so far.

 

[anojones]

There are some issues insulating a metal sided shop that will be heated, the warm air inside will allow water to vaporize and move through the insulation to the inside of the metal siding and condense there causing moisture (insulation can become wet etc). Moisture that does move through can get trapped in the insulation and along the walls. This is the great advantage of the spray on foam- no moisture can move through and condense on the walls as you have essentially coated the metal. There seem to be two schools of thought when using fiberglass in this situation- one is make sure you have a good vapor barrier on the warm side (inside the shop) of the fiberglass so moisture can't move through and get into the insulation. The flip side of that is that you can't ever have a completely sealed vapor barrier and some moisture will get in, thus some say not to put in a vapor barrier so that moisture that does get in can vaporize and move back and forth freely. In a house that uses fiberglass, the siding and housewrap allow any moisture that moves into the walls to move out through the house wrap and siding, but metal is not permeable in the same way. That being said, I insulated my shop with fiberglass batts and put up a 6 mil vapor barrier sealed with tape- inexpensive and effective and do not have moisture problems that I am aware of. If you can keep the insulation from touching the metal siding so much the better- any moisture that forms on the metal won't soak the insulation. The spray foam has some advantages of keeping wind out, no nesting for critters and reportedly stiffens up the whole building. You also have to think about your climate, high humidity worsens the moisture movement and I don't have that where I live.

 

[Dishpointer]

I live in the same area as you and I insulated our 40X 60 X 12 Shop with spray foam on all walls and 14" of blown in cellulose in the ceiling. The interior is finished off with white metal like the above picture. Although the cost of the foam was higher than the other options, it was the best option for me. It made the walls more rigid, it doesn't have the condensation problem that other insulation has because of contact with the exterior metal walls, and it seals all air gaps. I just installed a 100K btu propane furnace this week and it will heat the shop up from 45 deg to 60 deg within 10 minutes and the furnace won't kick back on for 30-40 minutes. And that's with an outside temp in the mid 20's!
If I were to do it all over again, I would definitely use spray foam again. It does cost more up front but the energy savings are worth it.

 

[raasd]

Our shop is insulated with fiberglass batt, but if we had to do it over again, spray foam all the way. we have in floor heat which is the way to go if you ask me. We can keep the shop about 10 degrees cooler and it still feels warm. You can lay on the floor and not get cold, and your feet don't get cold. It is efficient and effective. Our shop is 40X60.

 

[crbr]

Spray.

Much more advanced in efficencies gained. A superior product.

 

[monteu]

It seems that spray foam has the most votes! This will cost 6 to 7 times what the rollout fiberglass insulation, 5x more than polystyrene with foil back, and 2x more than RMax insulation board with foil back. I actually have a friend here that does spray foam for a living and I know he would do a good job. It is just that when I am getting a loan to build this shop is it wisdom to spend that much extra on insulation? It just might be.