Air sealing a new build (Building Science)

[8mpg]

So Im working on a new build and have done a lot of research into building science for houses while I did a full gut remodel on my house. Air sealing and a continuous insulation layer are vital to get an efficient building. Im going to stick build my building and was planning on zip sheating (possibly ZipR with 1/2-1" foam for the continuous insulation). Im looking at a much more expensive sill seal (cost is only about $150 more) but started to worry about building too tight as it is just a shop and not going to be air conditioned or heated.

Should I really spend all the time/money/effort to maximize the air sealing and the continuous insulation? I have a feeling the ZipR sheathing is going to be at least twice the price of standard Zip. I may spray foam the walls and roofline if I don't do the ZipR sheathing.

 

[RVDan]

Sure. Insulate and seal as good as you can afford.

 

[850xpeps]

A shop will hAve overhead doors which leak. I wouldn’t worry about being too tight.


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[Musicinabottle]

Totally agree with the others. Bolt it tight as you can. You couldn't possibly regret it.

 

[matt_i]

Instead of the rigid foam sheathing, are you looking at 2x6 framing or "better" windows and doors?

Tightening up a building is important for efficiency but I don't get why you'd spray foam and then have no HVAC...I get the "its just a shop" but I like to spend time in mine when its hotter or colder than I'd really like

 

[Jlbc212]

If you are stick building, fiberglass batt insulation is much less expensive than sprayed in foam. IMO any insulation placed on the exterior of the sheathing has the potential for trapping moisture in the sheathing.

 

[old__man]

So you want an efficient building that is really well insulated but you are not going to heat or cool it? I am try to understand what it is you are trying to achieve.

 

[laser3kw]

Instead of the rigid foam sheathing, are you looking at 2x6 framing or "better" windows and doors?

Tightening up a building is important for efficiency but I don't get why you'd spray foam and then have no HVAC...I get the "its just a shop" but I like to spend time in mine when its hotter or colder than I'd really like

Build it with future intentions in mind.
I insulated mine as tight as I could. Here, 5 years later, I still have no heat. But, it will be 25° in there when it has been below 0 for a week or more. And when I fire up a space heater, I can still raise the temp to a comfortable level in a couple of hours.
I do intend to heat it ... some day!

 

[Doug B]

8mpg, tell us generally where you are located(even just what State), and how the shop will function for you( woodworking,auto shop, daily driver parking,etc.)

 

[8mpg]

8mpg, tell us generally where you are located(even just what State), and how the shop will function for you( woodworking,auto shop, daily driver parking,etc.)

This is just a home shop here in North Texas. Mostly auto and welding type work.

For all the guys asking why insulate and not a/c and heat...The insulation will make the temps much more mild than if it were not. My garage is insulated and when its 100*f outside, its mid 80s. My old garage wasnt and it got hot when it was hot outside and cold when it was cold.

 

[theoldwizard1]

My daughters father-in-law is a certified energy consultant. He built a new house a couple of years ago using Zip System sheathing. It also had double width 2x4 walls and all of the "extra" sealing he could put in it.

The biggest problem with building like this is lack of FRESH air. If you cook in it, the smells can last days. Think what it would be like after a poker night with guys smoking cigars, drinking beer and eating pickled eggs !

An air exchanger (heats cold outside air as it enters with the warm inside air you are expelling) is a must.

 

[stm317]

An air exchanger (heats cold outside air as it enters with the warm inside air you are expelling) is a must.

Maybe in a house, but how critical is that in a garage with massive, roll-up doors that don't seal perfectly?

I'd say insulate the building as well as your budget allows. Going to great lengths with the latest in green building techniques might not be worth the cost in a detached garage. More traditional building techniques with adequate insulation will work just fine to moderate temps in the shop. Obviously, conditioning the space would help a ton, but that's your call.

 

[d300]

I would spray foam the entire structure with a minimum of 3" closed cell and skip the Zip stuff. The foam will seal every nook and cranny and you will not have any air movement. Heat it with a candle and cool it with an ice cube......

 

[GTO]

I would never seal any structure 100%
Living space or not.

 

[jabin]

8mpg, Building science is really changing and you're on the right course. No doubt, you would or will enjoy Matt Rissinger's Youtube channel (he's in Texas).

Insulate the most you can afford, the Advance zip with exterior foam board insulation is better than just the spray foam and is an excellent thermal break and moister barrier, IMHO.

Closed cell spray foam will not give you the same results as your current plan. Since your heat and humidity are on the outside 10 months out of the year, your exterior vapor and moisture barrier are supper important to get right. No doubt you know that 2 vapor and/or moisture barriers are a no,no and will equal rot.

Your insulation will keep is cool during the heat of the day, as you pointed out and fresh air is not as relevant as if this was a living house, but even then you would install a air exchanged that would allow to you control and condition the air exchanged. You could open the garage door at night to bring in fresh air, when desired.

The IBS show was pretty amazing with new exterior finishes and more data, but your choices really open us since you handled the moist barrier with advancedZip.

Your biggest thermal issue will be your roof, are you also using insulated panels up there? Combined with metal roof on angled slates for hot air venting and moisture draining gives you a cooling and drying roof.

 

[ard]

I would not skimp or cut corners on stuff that you can never really go back and upgrade.

In 10 years you can drop a small heater in there and have a great workspace. As opposed to "hey do you guys think a heater is worth it, I built it like a sieve thinking Id never heat it- now what?"



Also, keeping heat out- when you have many days over 100F, is not to be overlooked. Workimng in a 80, 90F 'shop' is WAY different than a 110 'oven'!

 

[8mpg]

Thanks for the replies guys..

jabin - I have been really interested in this stuff for the last few years. Just ran into Matt Risingers video today about drywall gasket from Dow which I will definitely do (its cheap). I agree Zip is the way to go not only for air sealing but a great moisture barrier. Im planning on using a liquid flashing to seal the zip to the foundation. I also plan on using zip sheathing for the roof. Honestly didnt think about doing the Zip R for the roof though but it makes sense. I need to get some quotes on materials.

 

[James-W]

I really don't get the insulation thing since you aren't heating cooling the space. Normally people want insulation to keep the heating/cooling costs down. There is a payback to having insulation, that is to say, it costs a certain amount of dollars to install insulation but you save a certain amount of dollars as the years go by. At some point down the road the cost of the insulation is paid for by the savings on heating/cooling bills and from that point on you continue to save money. But in this case I don't see the logic to it. Maybe I just can't see the forest for the trees but for some reason it has me baffled. Could you please enlighten me?

 

[850xpeps]

If I were to stick from my building I would 2x6 the walls and then fibreglass batt, vapour barrier sealed very well. And then r50 blow in cieling.

When I build my shop it will be icf walls netting r25 with no thermal break and no air penetration, and r50 blow in cieling. I won’t seal won’t with foam in a space that might be in contact with lots of moisture. Save the money and fibreglass bath and vapour barrier. Accoustical seal the vapour barrier and if you reall want install a thin layer of rigid insulation on the inside to remove a thermal bridge.

Even at our cold temperatures of -30 Celsius my dads garage with r20 batt and vapour barrier stays surprisingly warm inside with the warmth of the vehicle.

 

[fritz4545]

The Zip with insulation is expensive, we are using it on a project in Austin and the Zip with 1 1/2" insulation is 66 dollars a sheet. This was bulk price, about 3400 sheets. The joint tape is also costly, about 50 cents a foot.

 

[cajunfirehawk]

Texas heat and humidity is tough, my biggest question; is Zip and ZipR popular in TX or just the northern part of the country? But on the other hand spray foam is VERY popular in this part of the country, there must be a reason if one is more popular in this region? I'm just asking?

 

[walrus]

My daughters father-in-law is a certified energy consultant. He built a new house a couple of years ago using Zip System sheathing. It also had double width 2x4 walls and all of the "extra" sealing he could put in it.

The biggest problem with building like this is lack of FRESH air. If you cook in it, the smells can last days. Think what it would be like after a poker night with guys smoking cigars, drinking beer and eating pickled eggs !

An air exchanger (heats cold outside air as it enters with the warm inside air you are expelling) is a must.

Open a window? How much energy does a air to air heat exchanger use? Also cost to buy and install, I guess its automatic so you don't notice it but open the window seems like a money saver once you find out costs of ducting and unit

 

[8mpg]

I really don't get the insulation thing since you aren't heating cooling the space. Normally people want insulation to keep the heating/cooling costs down. There is a payback to having insulation, that is to say, it costs a certain amount of dollars to install insulation but you save a certain amount of dollars as the years go by. At some point down the road the cost of the insulation is paid for by the savings on heating/cooling bills and from that point on you continue to save money. But in this case I don't see the logic to it. Maybe I just can't see the forest for the trees but for some reason it has me baffled. Could you please enlighten me?

Again, working in an 80*f shop while its 100*f outside is way better than 100*f shop. Same goes with the cold. Just because you arent heating/cooling doesnt mean it cant be more comfortable.

The Zip with insulation is expensive, we are using it on a project in Austin and the Zip with 1 1/2" insulation is 66 dollars a sheet. This was bulk price, about 3400 sheets. The joint tape is also costly, about 50 cents a foot.

I know its not cheap. Im expecting $40/sheet for the thinner 1/2" insulation version. The key is the thermal bridging you can avoid. It may be cheaper to just add my own 3/4" foam to the outside under the siding.

Texas heat and humidity is tough, my biggest question; is Zip and ZipR popular in TX or just the northern part of the country? But on the other hand spray foam is VERY popular in this part of the country, there must be a reason if one is more popular in this region? I'm just asking?

Zip is pretty popular here in Texas and probably most of the US due to how quick you can get a building dried in. I dont think Zip R with the attached insulation is as popular. It has much better air sealing capabilities than foam. The idea is to keep the air from getting in to begin with. Joe Lstiburek (father of building science) explains it really well when he says something along the lines of "would you rather your coat and have it between your ribs to keep you warm or wear the coat". Same applies to houses/buildings.

 

[850xpeps]

Open a window? How much energy does a air to air heat exchanger use? Also cost to buy and install, I guess its automatic so you don't notice it but open the window seems like a money saver once you find out costs of ducting and unit

Hrvs aren’t much money and burn little to no power running. They are usually auto with the furnace as well as hooked to humidistat. Connected to washrooms. Pulling the warmth from the air before it’s pushed outside and transferring it to the cold air coming in.

 

[jpmmilner]

I’ve worked on super insulated homes in the past (SIP panels, ICF basements, and efficiency all around), and I’ll say this. Insulation and air tightness is key to efficient comfort. I’ve always had the best luck with conventional framing with spray foam. These are externally tight. Inexpensive sheet foam panels at exterior, plywood or OSB on the corners for rigidity, and a good house-wrap (Tyvek) for draft-stopping (and a belt and suspenders approach). If you tape your windows in with a mastic tape to the housewrap and finish normally, you should be golden. I’ve done negative air testing on structures like this and the results are fantastic.

That said, I also agree: the garage door, even a good one, will leak like a sieve. Also agree that having a tight structure really requires that you think of how you will deal with fresh air. You said you would be doing mechanical work. Most shops I know of want or already utilize a welder, and you don’t want those fumes sticking around. Mechanical ventilation even as simple as a “fart fan” on a timer will make things a lot safer, and deal with the other challenge of extremely tight buildings, I.E. moisture sticking around and creating a great starting point for mold. Some mechanical vent elation of some kind is a must IMHO.


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[nes999]

I hate spray insulation. Its near impossible to run wires in a wall with it.

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[u3b3rg33k]

I hate spray insulation. Its near impossible to run wires in a wall with it.

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it's easy if you put in conduit before you foam!

 

[nes999]

it's easy if you put in conduit before you foam!

I'd rather not put conduit between every stud. You never know where things will move to in 20 yrs.

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[850xpeps]

I'd rather not put conduit between every stud. You never know where things will move to in 20 yrs.

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Wire the walls then spray foam...... if something is changing and for some odd reason your opening up walls in 20 yrs then use a router to cut in whatever extra wiring you want.

 

[8mpg]

Wire the walls then spray foam...... if something is changing and for some odd reason your opening up walls in 20 yrs then use a router to cut in whatever extra wiring you want.

Wiring before is the only way to go. Wire is cheap, add a bunch of extra circuits and outlets.