Page 1 of 2 12 LastLast
Results 1 to 15 of 24

Thread: Insulating an existing building

  1. #1

    Question Insulating an existing building

    Hey everybody,

    I've got an existing building I want to turn into a shop and just wanted to get some ideas on how to insulate/finish it before I started...

    The building -
    On a concrete slab
    35ft X 16ft stick built with 15ft ceilings - I believe the studs are 24in centers but I'm not sure - it was built by the previous owner so they may be some other odd spacing... there's also a vertical PT 4X6 every 8 feet instead of the 2X4 that would be there.
    Has exterior wood panel siding (5/8 inch) all around, one pedestrian door and a 15ft overhead door
    On the inside it's completely unfinished - just bare studs and the back of the wood panels - no insulation/house wrap/etc - and the wood panels obviously leak because there are a few studs that I'll need to replace due to water damage.
    There is also no ceiling - there are just trusses and open space right over the top of the walls - it does have a shingled, non-leaking roof that's in good condition
    It also has only one outlet so I'll have to run wire throughout the whole thing

    I want to end up with a completely insulated (heated/cooled with space heaters and a window unit) shop. It has no windows but I'm going to put in at least a few.
    I need some help figuring out the best place to start on getting it sealed up and insulated - it doesn't get terribly cold here but it gets pretty hot for several months and I'll want to keep it pretty cool so I'm looking for the biggest insulating bang for my buck. Spray foam is outta my price range. I'm doing it all myself. I also thought about dropping down and framing a ceiling at about 8-9 feet high for the sake of having less space to heat and cool... but I'm not set on that either way - Pros? Cons?. My main problem is that there is nothing sealing the wood paneling from where I would put insulation and the wood paneling is obviously not water tight or wind proof. What's the best way to seal everything up before putting in fiberglass insulation? Seems like the ideal thing would be to completely remove all the siding, put up a house wrap and reinstall the siding - that's obviously not something I want to do.

    Any ideas or suggestions are appreciated...

    Jack

  2. #2
    Join Date
    Feb 2012
    Location
    Haubstadt (Evansville), Indiana
    Posts
    1,294
    I can only comment on the ceiling. I would put in a ceiling, but not do less than a 10' ceiling.

  3. #3
    Where are you located, and are you pulling a building permit, and do you want the slab as your floor surface?

    You need to tackle the leaking siding first. Is the current siding/sheathing like a T-111 product? If so, there is no need to remove it other than repairing any rotten or leaking areas. If you want to add siding, you can do so right over it. There are several ways to proceed from here concerning insulation... Adding a layer of rigid XPS on the exterior under your siding which can be applied directly on top or use a rain screen approach furring it off the building. The slab will need some type of isolation from the exterior which may mean running vertical panels of rigid XPS around the exterior of your foundation down at least 2', depends on your answer above. Interior I'd use Roxul insulation, cost is close to fiberglass but has higher r-values and moisture, airflow and insect resistance. If you dont do the rigid over the exterior sheathing, you can do so on the inside. 10' or higher ceilings in a shop is ideal, 9' at a minimum. Think about wacking a light with a long board or sheet of plywood.

    Thats all I've got for now, pics would be helpful and answers to above.
    "The real voyage of discovery consists not in seeking new landscapes, but in having new eyes." - Proust

  4. #4
    I also made a shop out of an old pole building that was here when I bought the place. With the extra height you have, I'd consider building a floor system above the 10' ceiling that would be your ceiling. The building is only 16' wide, so you could use 2x10's on 16" centers, floor it and use it for storage, or even more. You can still attach your ceiling under it, just make use of the space above. If your south wall is open, I'd put some windows there to help heat in winter, and ventilate spring and fall. Need an opening on the north to allow the air to flow through. Personally, I believe in boxing, I'd probably take the siding off and put waferboard on the studs, housewrap over that and siding over the top. If you check the existing siding, it's probably shot, as that stuff has about a 15 year life.

  5. #5
    A few things come to mind. First, dollar per R-value, it's hard to beat fiberglass insulation, esp. for a DIY project, and in a mild climate. Since heat rises, most heat loss is from the ceiling, so put as much there as you can. Also, since roofing material is usually a darker color than siding, and facing more skyward, roofs absorb more heat in the summer, so more heat would pass into your ceiling (per sq ft) than the walls.

    As far as ceiling height, I'd personally go with higher ceilings. First, it would give you a lot more storage space- you can store long pieces of lumber and plywood vertically, if you wish, and install taller shelves or cabinets. Second, it makes it easier to wrestle around tall or long projects (say a wall unit/tall bookcase) without worrying about hitting the ceiling. The change in heat loss due to increased height is probably not all that great- again, the ceiling heat loss would be the same, so the only difference would be the increased area from the perimeter walls.

    You mentioned that your overhead door was 15 feet, which I assume is the width. If it's the door height, though, you're obviously locked into a 15+ foot ceiling to clear the track, or else drop the ceiling behind the track, which seems overly complicated.

    Installing a ceiling is better for insulating than leaving open and insulating between the rafters. If you do so, make sure you ventilate the "attic" above the ceiling well. To reduce heat gain in the summer, really consider installing an attic ventilating fan in the roof.

    As far as siding, others have already recommended finding the water damage source, and ideally enclosing the building with sheathing and house wrap. That is a pretty big undertaking, and it might not be worth the effort, if you can otherwise eliminate the cause of your water damage. There are a lot of factors to consider, such as weather exposure and climate. Do you get a lot of wind-driven rain, that could penetrate the siding and cause internal damage? One reason for house wrap such as Tyvek is to act as a moisture barrier to outside water, while still letting water vapor to escape from the interior. I'd say if you're going to pull off the siding anyway, go ahead and sheath and house warp. One alternative would be to consider the current siding as a sheathing of sorts, wrap over it, and put a new siding over the wrap.

    It sounds as though you live in a mild climate, so water vapor escape isn't an issue because: 1) water vapor is a problem in cold climates, since in will condense (and freeze) within the walls, causing water damage and reducing insulating capability; most household water vapor is generated from activities such as cooking, showers, laundry and the like, which you're not likely to do in your shop.

    If you plan on covering the interior side of the walls, I think it's pretty hard to beat plain old drywall in terms of dollars/square foot. Good luck- I'd love to have that much space for a shop!

  6. #6
    Quote Originally Posted by James Conrad View Post
    Where are you located, and are you pulling a building permit, and do you want the slab as your floor surface?

    You need to tackle the leaking siding first. Is the current siding/sheathing like a T-111 product? If so, there is no need to remove it other than repairing any rotten or leaking areas. If you want to add siding, you can do so right over it. There are several ways to proceed from here concerning insulation... Adding a layer of rigid XPS on the exterior under your siding which can be applied directly on top or use a rain screen approach furring it off the building. The slab will need some type of isolation from the exterior which may mean running vertical panels of rigid XPS around the exterior of your foundation down at least 2', depends on your answer above. Interior I'd use Roxul insulation, cost is close to fiberglass but has higher r-values and moisture, airflow and insect resistance. If you dont do the rigid over the exterior sheathing, you can do so on the inside. 10' or higher ceilings in a shop is ideal, 9' at a minimum. Think about wacking a light with a long board or sheet of plywood.

    Thats all I've got for now, pics would be helpful and answers to above.
    Located in southern Arkansas - gets pretty hot for several months and really humid, gets sorta cold (down to the teens) for a little while but not long. No permits. I would probably prefer the slab as the floor - maybe put some sort of sealant on it to cut down on concrete dust and what not. I think the relatively mild climate means I can probably forgo any insulation of the slab correct?
    Yes, it is a T1-11 type product... I just didn't know what it was called

    So I could put XPS directly over the T111 then put up some sort of siding over that? Or would I wrap the entire thing with Tyvek then put the XPS then the final siding? I guess the XPS with the seams taped would be a water barrier?



    Quote Originally Posted by John Donhowe View Post
    A few things come to mind. First, dollar per R-value, it's hard to beat fiberglass insulation, esp. for a DIY project, and in a mild climate. Since heat rises, most heat loss is from the ceiling, so put as much there as you can. Also, since roofing material is usually a darker color than siding, and facing more skyward, roofs absorb more heat in the summer, so more heat would pass into your ceiling (per sq ft) than the walls.

    As far as ceiling height, I'd personally go with higher ceilings. First, it would give you a lot more storage space- you can store long pieces of lumber and plywood vertically, if you wish, and install taller shelves or cabinets. Second, it makes it easier to wrestle around tall or long projects (say a wall unit/tall bookcase) without worrying about hitting the ceiling. The change in heat loss due to increased height is probably not all that great- again, the ceiling heat loss would be the same, so the only difference would be the increased area from the perimeter walls.

    You mentioned that your overhead door was 15 feet, which I assume is the width. If it's the door height, though, you're obviously locked into a 15+ foot ceiling to clear the track, or else drop the ceiling behind the track, which seems overly complicated.

    Installing a ceiling is better for insulating than leaving open and insulating between the rafters. If you do so, make sure you ventilate the "attic" above the ceiling well. To reduce heat gain in the summer, really consider installing an attic ventilating fan in the roof.

    As far as siding, others have already recommended finding the water damage source, and ideally enclosing the building with sheathing and house wrap. That is a pretty big undertaking, and it might not be worth the effort, if you can otherwise eliminate the cause of your water damage. There are a lot of factors to consider, such as weather exposure and climate. Do you get a lot of wind-driven rain, that could penetrate the siding and cause internal damage? One reason for house wrap such as Tyvek is to act as a moisture barrier to outside water, while still letting water vapor to escape from the interior. I'd say if you're going to pull off the siding anyway, go ahead and sheath and house warp. One alternative would be to consider the current siding as a sheathing of sorts, wrap over it, and put a new siding over the wrap.

    It sounds as though you live in a mild climate, so water vapor escape isn't an issue because: 1) water vapor is a problem in cold climates, since in will condense (and freeze) within the walls, causing water damage and reducing insulating capability; most household water vapor is generated from activities such as cooking, showers, laundry and the like, which you're not likely to do in your shop.

    If you plan on covering the interior side of the walls, I think it's pretty hard to beat plain old drywall in terms of dollars/square foot. Good luck- I'd love to have that much space for a shop!
    The overhead door is actually about 15 ft (give or take) TALL and 15 ft wide (the whole end of the building is a huge overhead door.... it was made for a large RV. I plan to remove the whole thing, frame in the wall and put either a set of double doors or a smaller roll up door.

    I think I'm leaning towards a tall ceiling like you said -- I can always use the upper 3-4ft of the wall for storage of things that aren't used often and I like the idea of being able to stand up a 10-12 ft board vertically if needed.

    The source of the water damage isn't a mystery... the building is so tall that it's very easy for rain to blow against the wall, especially at the bottom. The bottom couple of inches of a few panels is somewhat rotten. There's also one short sill plate by the pedestrian door that I'll have to replace. Part of what I'm trying to figure out is how to best waterproof the exterior before finishing it out.

    Thanks for all the suggestions so far and I'll try to take some pictures tomorrow if the weather lets up....

  7. #7
    With no permit, you can do as you want. Just think of that slab as a giant heat sink, but it is something you can add later. No need for house wrap with the XPS, just tape the seams and shiplap or T&G product is better with the tape. It also acts as a thermal break. My barn had a similar exterior rated product, 2x4 construction, 26x32 with a 1/2 story. The exterior was in good shape and I plan on adding siding over it next year. I used Roxul R15 walls and unvented R30 roof with 1/2" R3 XPS throughout the interior with 5/8 CCX plywood covering, except my workbench area has 3/4 v-match, looks nicer. While we don't have extreme heat in the summer, ocean humidity is normal, teens is normal winter lows. Without heat/AC this summer it was consistently 10* cooler and less humid in the building, the heat pump will go in next month. That thermal break and vapor retarder that the XPS provides makes a huge difference.

    If you put the XPS on the exterior, you may need to add nailing strips around your doors and windows to match the thickness of the XPS to be able to secure them and trim. Defiantly get rid of that roll up door if its of no use to you, very hard to seal those doors well. I used an 8' slider on one side and a 9' French door on the other with 3' fixed panel and 2 in-swing for the 6' entry. I wanted to do 8' tall doors for even more light but the existing framing was just a tad too low and it was easier to frame down to the normal 68 tall RO.

    I put all of my outlets and switches at the same height, about 48", window sills just a bit lower. Leaves room for benches/machinery under them and was easy to break the wall covering there too.
    "The real voyage of discovery consists not in seeking new landscapes, but in having new eyes." - Proust

  8. #8
    Join Date
    Jul 2003
    Location
    Winterville, NC (eastern NC)
    Posts
    2,360
    I repurposed a bldg. similar to yours, with the 4 X 4 posts every 8 feet. I framed between these posts with standard 2 X 4's, put R-11 between the studs with the paper facing the interior. Another trick I saw in Fine Homebuilding magazine was to seal the joint between the exterior siding and the framing with caulk. Do this in each stud cavity to block any stray outside air leaks from invading your interior.
    Another comfort item I plan to tackle soon is to close in the open attic area of the shop. I plan to install a drop down attic stair unit to access the valuable storage up there, and place insulation between the ceiling joists, followed by paneling. Some new light fixtures and my shop sanctuary will be more comfortable.

  9. #9
    Yeah, I think I'll go with the XPS - one my main problems down here is the humidity and every pc of bare cast iron will rust instantly depending on the day so I really need something to cut down on the humidity or at least keep it a more constant level inside the shop.

    I guess I could XPS the exterior re-apply some TG panels then caulk the inside and put in fiberglass rolls between the studs and be set to cover it with OSB or whatever.

    One more - what is the advantage, or disadvantage, of insulating right up against the roof decking rather than dropping down flat, blowing insulation on the ceiling and having a vented roof? The roof on mine doesn't have a soffit at all... the walls just stop and it's completely open between the top of the wall and the roof decking. If I just do an unvented roof will that save me the trouble of putting in a soffit and venting it?

  10. #10
    If you add insulation to the ceiling or roof, you have to have ventilation, as the insulation collects moisture where the temperature difference meets. That is why attic spaces are ventilated.

  11. #11
    Quote Originally Posted by Jim Andrew View Post
    If you add insulation to the ceiling or roof, you have to have ventilation, as the insulation collects moisture where the temperature difference meets. That is why attic spaces are ventilated.
    Someone mentioned an unvented ceiling so I assumed they were talking about insulated the roof like you would a wall... sort of like the roof of a mobile home where the roofing/insulation/ceiling material is all stacked right together and there is no space between the insulation and roofing. If that makes any sense at all.

  12. #12
    That was me, however, since you get extreme summer heat there is a possibility of shortening the life of your roof shingles with an unvented application. There have been several studies done that show, even with ventilation in a cathedral ceiling application, under roof temperatures are often the same in an unvented situation. Going this route, you really need to seal the rafter bays very well and use a dense insulation.

    In a standard attic situation, where there is a space between your insulated cieling and roof, typically ventilation is important with either a soffit/ridge vent or gable vents to regulate the temperature of the space and remove any moisture transferred from the living space below and normal heat/cool of the day.
    "The real voyage of discovery consists not in seeking new landscapes, but in having new eyes." - Proust

  13. #13
    Ok... so you'd definitely recommend going with the typical attic situation where I install ceiling material on the bottom of the rafters, put good insulation on top of the ceiling then make sure there are at least one type of venting in the attic?

    I'm still kind of leaning towards framing in the ceiling at about 9-10 feet rather than the full 15... the difference is heating and cooling an extra ~2500 cubic feet of air every time I want to cool it off or heat it up... IF I'm thinking correctly.

  14. #14
    You are exactly right about the extra space to heat and cool. And when you get moved in and working in the shop you will find you wish you had more storage space. That is why I suggested building your ceiling strong enough to support a floor and storage upstairs.

  15. #15
    Quote Originally Posted by Jim Andrew View Post
    You are exactly right about the extra space to heat and cool. And when you get moved in and working in the shop you will find you wish you had more storage space. That is why I suggested building your ceiling strong enough to support a floor and storage upstairs.
    I've considered the storage space up top... I'm just not sure if I could make it strong enough to hold all that weight without having to have support poles in the center of the building. Wouldn't I need some support in the middle of those 2X6's that span the 16ft width?
    And the siding is actually in good shape everywhere except the few places where it's been exposed to tons of water and is rotten... no damaged areas at all above about 6 inches from the ground.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •