I am working on re-insulating a shed (350 sq. ft.) that has been used as a workshop. It has T1-11 siding and 2x4 walls. I've taken down all the interior paneling and had electrical updated. Now, to insulate before drywall.

Most of the T1-11 exterior siding will need to be replaced, and spray foam in place is not in the budget. What is the best way to increase the R value and should I put a vapor barrier on top of the insulation before drywall?

When I eventually replace the siding, I will use Tyvek on the exterior so unsure as to the best way to insulate the interior - will R15 paper-faced be enough?

I live in Maryland - temps can range from 10 - 95. I plan to use the building as an office and workout space. Thank you!

  • What are you using the shed for? Will it be heated and/or cooled? Where in the world are you (your climate matters)? These are important details for knowing whether R-15 is enough and if paper-faced is a suitable vapor barrier. Please edit this info into your question so it's more obvious for everyone to see.
    – FreeMan
    May 26 at 13:07
  • 1
    Your two questions are vague and subjective--"best" and "enough" aren't something we can decide. Please revise to ask something specific and clear.
    – isherwood
    May 26 at 16:29

2 Answers 2


The best way to increase insulation is to have more of it.

You can combine batt or cellulose in the small cavities with foam sheets overlaid under the drywall (reduces interior space) or under the siding - that adds more insulation and also breaks the thermal leak path through the studs. An unlikely approach for a 350 square foot shed (but you need new siding anyway) would be to build the walls out via "Larsen trusses" to make more space for insulation (which can be nice inexpensive, but highly effective, cellulose, where vapor barrier is optional.)

Vapor barrier, if any, goes on the warm side. If you heat but don't cool, that's the inside. If you do both it becomes nuanced.

  • That makes dense cellulose with Larsen Trusses look really attractive IMHO.
    – Ecnerwal
    May 26 at 13:13

This is what I did; I put Tyvek on the exterior studs, taped the seams and then I put strips of pressure treated fencing board over the studs to create a gap between the T1-11 siding and the Tyvek. Then insulate in between the studs before I put the T1-11 siding. Normal vapour barrier and drywall on the inside.

Shed is 9'*12'and the temperature is about 15C warmer then the outside temperature, with me and about 150Watt of power usage from electrical equipment. (Nearly all electricity, except for light going through the window is eventually heat) In winter most of the time I can comfortably heat the shed with an additional 200W electrical heater running full time)

  • An opportunity for seasonal bitcoin (or whatever) mining ;-) - getting cold, fire up the servers. Just don't make them too big.
    – Ecnerwal
    May 27 at 14:25

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