Keep my garage moisture free

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from Google/wikipedia:
In construction, furring (furring strips) are thin strips of wood or other material to level or raise surfaces of another material to prevent dampness, to make space for insulation, or to level and resurface ceilings or walls.Furring refers to the process of installing the strips and to the strips themselves.

Exactly!
 
I’ve been told by a metal building supplier that over time, the spray foam will trap moisture between it and the walls and cause the building to rust.

It did a big commercial bldg. I worked in one time , then the spray foam started falling off--------jfi
 
Disclaimer: I'm not anywhere near a building professional, and am barely skilled at building related stuff. But I have done a ton of looking into these things over the past several years as we've remodeled on of our houses and have been working on using our barn for shop activities.

Insulation and sheathing aren't lightweight. Before doing anything I'd ask your building mfg what kind of loads the uprights can take. You may need additional framing (wood or metal) in order to adequately hold up additional mass. The amount of weight that the current framing can hold will determine your available options. Doesn't matter if you can get an r45 wall for $600 if the weight will tear your walls down.
Next, you'll want to know what kind of weight your foundation footer was designed for, because additional framing may help hold more insulation, but if the footer can't take it, then it's moot.

With those constraints sized, you can look at what your feasible options are. How much insulation you need will depend on your goals and climate. R6.5 won't do you much good if you gotta deal with temps under 0, and still may not prevent condensation. Designing an insulated envelope can be tough because you need to constantly keep the interior temperature above the ambient dew point. The more humid your location, the higher the temp needs to remain.

A radiant backing between your metal surface and the backside of your insulation (foil backing) is a good idea. Metal conducts heat quickly and radiates heat much better than wood building materials. You want to ensure that the foil ix permeable though, or that you keep a gap between the back of the insulation and the metal wall so that air can circulate. Even spray foam can absorb water where there are seams and "laps". A good installer can prevent them, but any joints where new spray overlaps cured or partially cured foam can trap water vapor, which becomes standing water.

Since your walls are corrugated, airflow behind the insulation should be easy. The job of your exterior sheathing is basically to keep rain and snow off your insulation, and thats about it. Which means your insulation and any interior sheathing should be sealed to the floor and create one sealed interior envelope. Which also means you want to insulate over the metal beams, not necessarily between them. You can add additional insulation in those cavities, but it will only be marginally effective since any exposed metal will be a point of condensation and will also rob heat from your interior space. If your interior isn't a sealed envelope, warm air will carry water vapor into any place there's an air leak and you'll eventually be dealing with water damage. Even if your materials are waterproof, you may still get mold or bugs, which are no less troublesome. Ants have been known to burrow into foam and even rockwool to make nests. Birds eat ants and like wool-like materials for nests... You can see where this goes.

You can use almost any heat source which vents combustion outside. Direct fired heat sources don't do this, but there's plenty of cheap furnaces or wood heat which will fit the bill. Even an oil burner will do. Just needs to exhaust outside to carry away the moisture. Radiant floor heat is probably one of the best you could install for a shop, but it's typically tough to do after the slab is already poured. Wood fired boilers, heat pump water heaters or any other means of creating heat can be used with it for max efficiency or convenience. You can use electric floor heat, buts it's far less efficient compared to a heat pump driven radiant system.

Polyiso sheets tend to be cheap and if you use two layers (2" ea), staggered. It's possible to get a very tight envelope that should exceed r15 in many cases, which is close to residential requirements in some places. Even rockwool will need sheathing, and probably costs more per square foot than poly iso, and will also require more framing to hold it to the walls since it's made for typical wall cavities (based on what I've seen). Polyiso is also commonly available with a radiant barrier on one side (foil faced) which is still an excellent thing to have in a metal building.

Just my $.02

so it would be better for me to install the panels over the existing metal framing, then fasten the insulation panels to the framing, rather than installing insulation panels between the framing?
 
My building is 720sqft, would two small box fans from the local home improvement store be enough? I would like A/C but anything greater than a window unit would be unlikely.
Yes , as long they are on 24/7 . THat will stabilize the moisture content allowing you to control the humidity
 
It did a big commercial bldg. I worked in one time , then the spray foam started falling off--------jfi
Im hoping that was years ago. There weren't many guys applying it, or even certified to do so.
The products in use now seem to be pretty damn good, plus the application process has evloved.
 
Im hoping that was years ago. There weren't many guys applying it, or even certified to do so.
The products in use now seem to be pretty damn good, plus the application process has evloved.

The fiberglass, thick plastic skinned ins. that bldg. companies install has proven to be the best around here , working in and out of and on those bldgs for 52 yrs. influences my opinion ------
 
so it would be better for me to install the panels over the existing metal framing, then fasten the insulation panels to the framing, rather than installing insulation panels between the framing?

Yes. Between can work, but it will have multiple drawbacks. Heat will be conducted in/out by the metal framing, but worse it will allow condensation to form at the edges of some of your insulating panels. This can draw bugs and mold etc.

One sealed envelope will help seal the wind out and will also be a neater install in my opinion.
 
Yes. Between can work, but it will have multiple drawbacks. Heat will be conducted in/out by the metal framing, but worse it will allow condensation to form at the edges of some of your insulating panels. This can draw bugs and mold etc.

One sealed envelope will help seal the wind out and will also be a neater install in my opinion.
Darn, what sucks is I already have my electrical installed over my framing.

AEBF9DA4-DD51-44F2-86C9-1A07B2FACBDD.jpeg
 
Pole building 40x60x12 that bubble wrap under the metal siding and roof. 6x6 beams 8 ft on center. I put 2x6s 4 ft between beams then used 6” thick fiberglass battens 24” wide stapled together to make 4ft then 1/2 osb ply over that osb in the ceiling but no insulation up there yet. Still get a little moisture in the summer so I’m thinking of some type of air flow (no windows) 80 thousand btu oil furnace and two 110 ac window type units on each end of building. I can keep it 70 year round in Va
 
cut the rigid boards and stuff them between the uprights then foil tape the seams , if you make them tight enough no need to fasten them in place . same for the roof then screws with large washers into the purlins ...done , easy peasy
 
Ok guys, after some additional research I think I have a plan for what I am going to do. I think I am going to use 1 inch polyiso foam boards (foil on both sides). And place them between the beams, while foil taping the exposed metal on the beams to prevent condensation (does that sound right?).

Once the foam boards are up, I plan on using a thick plastic vapor barrier to cover the foam board insulation. I’ll be insulating the walls first, and then the roof. Once the building is fully insulated, I plan on installing a wood burning heater along the back wall (the wall across from the large doors) towards the center of the wall so it can heat the shop evenly.

IMO this should be a relatively simple, cost effective way of insulating my shop.

what do you guys think?
 
When my pole building was built the contractor installed either 1/2” or 3/4” foil covered styrofoam between the wooden frame and the metal sheeting and fiberglass with foil backing between the rafters and the steel roofing. There is a vapor barrier under the concrete floor and the floor is sealed. I have no issues with moisture and plan on upgrading the insulation and installing a HVAC sometime in the future.
 
Another option is to space the boards away from your siding which would add an air space and the rigid boards themselves would not come in contact with the siding and condensation. Your roof has the purlins which will give you a 1¨ air space . Unfortunely due to the horizonally mounted siding you have no purlins on the vertical walls . After you cut your fitted boards you can glue several approx 4-6¨ strips of excess board material to the back of your fitted boards to give you a 1¨ air gap.
 
Another option is to space the boards away from your siding which would add an air space and the rigid boards themselves would not come in contact with the siding and condensation. Your roof has the purlins which will give you a 1¨ air space . Unfortunely due to the horizonally mounted siding you have no purlins on the vertical walls . After you cut your fitted boards you can glue several approx 4-6¨ strips of excess board material to the back of your fitted boards to give you a 1¨ air gap.
if I cut the boards to fit between the uprights on the walls I think I can wedge them between the framing. The tubing for the framework on the walls is 2inch. If I install the boards flush with the tubing on the inside of the structure, that should leave me 1inch of airspace behind the boards
 
Ok guys, after some additional research I think I have a plan for what I am going to do. I think I am going to use 1 inch polyiso foam boards (foil on both sides). And place them between the beams, while foil taping the exposed metal on the beams to prevent condensation (does that sound right?).

Once the foam boards are up, I plan on using a thick plastic vapor barrier to cover the foam board insulation. I’ll be insulating the walls first, and then the roof. Once the building is fully insulated, I plan on installing a wood burning heater along the back wall (the wall across from the large doors) towards the center of the wall so it can heat the shop evenly.

IMO this should be a relatively simple, cost effective way of insulating my shop.

what do you guys think?

You'll want a layer of foam over each exposed metal member, otherwise those cold beams will still sweat inside.

The idea of leaving a gap and securing directly to your framing is a good one, but the air space will act more like a "rain screen" and won't necessarily make the wall better insulated.

Since you have surface mounted electrical, I'd stick to your plan of going between beams (and overlapping a second layer over each beam). Later on you can add another layer and a few years later another layer... Etc.

Don't bother with the interior vapor barrier. The foil facing of the foam will act as one already (usually) and having the ability to diffuse any random moisture is still a good thing. Some sort of durable wall board would be a good idea to protect the foam boards. Plywood, osb, hardboard, drywall, concrete board, doesn't matter a ton, but any all-wood materials are at greater risk for fire than drywall (which actually produces moisture/water as it gets heated) or concrete board.

Since drywall sucks up standing water and is easily damaged, I like thin cement board for the first 4' or so of a garage wall.. But that's just me.


Another option would be to layer metal siding on the inside.. Durable, easy to replace, no mud or mortar to install it and can be taken down to augment your insulation in the future. Also less prone to fire/burning. Even corrugated metal roof panels could be used, even if only partially sheathing the wall.

Just my $.02
 
You'll want a layer of foam over each exposed metal member, otherwise those cold beams will still sweat inside.

The idea of leaving a gap and securing directly to your framing is a good one, but the air space will act more like a "rain screen" and won't necessarily make the wall better insulated.

Since you have surface mounted electrical, I'd stick to your plan of going between beams (and overlapping a second layer over each beam). Later on you can add another layer and a few years later another layer... Etc.

Don't bother with the interior vapor barrier. The foil facing of the foam will act as one already (usually) and having the ability to diffuse any random moisture is still a good thing. Some sort of durable wall board would be a good idea to protect the foam boards. Plywood, osb, hardboard, drywall, concrete board, doesn't matter a ton, but any all-wood materials are at greater risk for fire than drywall (which actually produces moisture/water as it gets heated) or concrete board.

Since drywall sucks up standing water and is easily damaged, I like thin cement board for the first 4' or so of a garage wall.. But that's just me.


Another option would be to layer metal siding on the inside.. Durable, easy to replace, no mud or mortar to install it and can be taken down to augment your insulation in the future. Also less prone to fire/burning. Even corrugated metal roof panels could be used, even if only partially sheathing the wall.

Just my $.02
I didn’t even think about putting small pieces of foam over the framing... duh haha

what do you mean by rain shield?

I like the idea of covering the insulation with something but I’m worried about the additional weight it would impose on the structure
 
I didn’t even think about putting small pieces of foam over the framing... duh haha

what do you mean by rain shield?

I like the idea of covering the insulation with something but I’m worried about the additional weight it would impose on the structure

Rain shield or rain screen is a term used to describe an exterior cladding that has an air space behind it. In contemporary construction it's done to prevent trapping rain or condensation between the cladding and the exterior sheathing or wind barrier. It can act as a radiant barrier space and also a thermal gap to prevent conduction from the framing to the exterior. The draw back is that it gives bugs a great hiding place and makes a wall assembly thicker for not a lot of gain in true insulation performance.

The weight of any interior wallboard is good to keep in mind. A sill plate could be bolted to the foundation and used to support the weight of the wall off the framing. Use good pressure treated lumber and it should last plenty long enough. As long as you're not framing a lumber wall to hold the interior sheathing, the slab should be sufficient to hold up the dead load it may impart. Metal siding would likely be the lightest per square foot and drywall (1/2 or thicker) the heaviest. You can look at lightweight drywall too, which is easier to handle if nothing else.
 
Rain shield or rain screen is a term used to describe an exterior cladding that has an air space behind it. In contemporary construction it's done to prevent trapping rain or condensation between the cladding and the exterior sheathing or wind barrier. It can act as a radiant barrier space and also a thermal gap to prevent conduction from the framing to the exterior. The draw back is that it gives bugs a great hiding place and makes a wall assembly thicker for not a lot of gain in true insulation performance.

The weight of any interior wallboard is good to keep in mind. A sill plate could be bolted to the foundation and used to support the weight of the wall off the framing. Use good pressure treated lumber and it should last plenty long enough. As long as you're not framing a lumber wall to hold the interior sheathing, the slab should be sufficient to hold up the dead load it may impart. Metal siding would likely be the lightest per square foot and drywall (1/2 or thicker) the heaviest. You can look at lightweight drywall too, which is easier to handle if nothing else.

Ah, ok

yeah, I have had bugs find their way into my shop. I bought some foam that is molded to the shape of the metal siding that I’ll be installing in all 4 corners of the shop to help prevent the bugs.
 
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