Methods to keep heat from infiltrating
hotwheels
| Posted in Energy, Heating & Insulation on
I have a storage building framed (2×4 walls 2×6 roof) and I want to insulate the walls and roof to prevent heat infiltration. The goal is to keep the interior of the building from getting too hot in my hot summers. Where I live in n.Calif. snow is not an issue although it gets cold for a couple of months.
Is there anything beyond just using fiberglass batts that would be effective to keep heat out of the building? I thought about riding foam, but that does not seem to offer much in the way of increased R value from what I found.
Thanks
Replies
riding foam??
caulk and seal ... joints, seams, cracks. Weatherstrip your door ... all FOUR edges.
Ventilate during cool evenings. ... may not be easy ... don't know your situation.
Bury it ... would work, but maybe not practical in your situation.
I was just thinking that keeping the heat out from the start may be the most effective--light colors or reflective materials to reflect radiant heat from sun. Once the heat has penetrated the exterior material (siding, shingles, sheathing) you are sort of stuck with it--insulation will help, but in my mind that puts your exterior between a rock and a hard place--heat comes in and then insulation keeps it there.
If it's just for storage, you might want to put up reflective foil faced foam on the underside of the rafters. Ideally you would have a continuous ridge vent, but if you don't, you can put horizontal strapping up so that air can go between the rafter bays. Same on the sides, but you don't need the space for the venting like you do for a roof.
By me, 4x8x2" polyurathane foil faced ridgid foam board was around $30 a sheet
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
I plan to install a ridge vent with eave vents so that should help. The foil based type radiant barriers combined with light colored reflective materials may help. I can also install rigid foam or batts, but I think the idea of the radiant barrier may be the key to the heat penetration issue.THANKS
With a ridge vent, you can just fasten the foil faced sheets directly to the underside of the rafters then. Screws and fender washers. You can get a foam gun to seal up the gaps between the sheets. This way you get actual R value in addition to the radient barrier.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
Remeber ... once the radiant barrier gets dusty/dirty ... it doesn't work very well ... which it will (get dusty/dirty). Don't rely on radiant barrier alone. The sales people that push the 'effective R-value' from radiant barriers are snake oil salesman.
There is evidence of the effectiveness of radiant barriers ... in laboratory or ideal testing. Don't konw about the agricultural applicaitons and the specifics of that.
Edited 6/2/2008 1:47 am ET by Clewless1
FYI ... foil faced foam is most commonly polyisocyanurate (polyiso) ... not urethane ... a close cousin. Thermax and R-max are common brands of this.
Urethane or polyiso is about double the insulation value over fiberglass (about R6.5-7.0 per inch while fiberglass is about 3.2, I think. Extruded polystyrene is 5.0 per inch. You need to protect both w/ fire barrier (i.e. 'sheetrock' or gypsum wall board).
In unattached storage I don't think he has the same fire covering requirements. If he does cover it with drywall as you suggest, and for general safety it's not a bad idea, then cross strapping with 2x2 to give the radient air gap would be required.
It sounds like this is the barn where he works on his cars.
As for dust, the top side will loose effectiveness at reflecting heat as air currents deposit dust, but the underside should stay fairly clean.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
I wish this was a place to put my car, but no just storage for some things that can benefit by not baking. I am also using the building as a way to learn how to build for my next project, which is a shop. For this building I plan to have a cathedral ceiling.How does this sound for a stab at minimizing heat in the buildingFrom the outside the roof/attic:
light colored shingles
roof underlayment
plywood decking with radiant barrier facing inside of building
air gap (ridge/eave venting)
(rigid foam???)
double bubble foil on the underside of the rafters
furring strips
drywallI am not sure about the value of using rigid foam or cellulose between the air gap and the bubble foam.Thanks!
JR
it sounds like lots of work for little effect
forget about the radiant foil and the double bubble packMike Smith Rhode Island : Design / Build / Repair / Restore
Mike,If there is going to be little effect, then simplifying things seems like a good idea. This web site shows the idea about using foil, furring, and insulation in a cathedral ceiling application ... maybe this just mean this for situations where the structure is heated and cooled?http://www.insulation4less.com/install_cathmethod2.asp
my only problem is i don't believe a single claim about reflective insulation being adequate for the job
other than that... what is simpler than dens-pak cells in the walls and 16" to 24" of cells in the attic ?
if you don't like cells... think about EPS foam, it has a lower R-value than other foams , but it's cost is way less too
i stay away from reflective insulations, bubble insulations , and fiberglass insulation
Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike , You did catch that this is a shed right?
They can't get your Goat if you don't tell them where it is hidden.
i did..... but heat gain is heat gain....
and insulation is insulationwhat is the reflective / bubble wrap going to do ?Mike Smith Rhode Island : Design / Build / Repair / Restore
From what i have read any radiant barrier insulation will cut down dramatically on heat gain due to solar gain. Doesn't matter if it is bubble wrap , foil film, or whatever is put up. Non are really more effective then any other, but all work better at that specific task the expensive alternatives of what i will call "real insulation"
They can't get your Goat if you don't tell them where it is hidden.
There is both a practical and a concept to sort out here for me: it is a shed/outbuilding, but because of what I plan to store in it, minimizing interior heat is important to me. The idea of a radiant barrier and radiant insulation seems to make sense since in a building where there is limited opportunity to address heat gain by using interior cooling. Minimizing the heat gain is then important, but I would think it is important in any structure. The concept is: how to minimize heat gain from sun exposure. The practical issue is what is the experience of folks who design and construct structures. Since I come to this unencumbered by knowledge or experience, the experience of those who know is valuable.At this point, I think some sort of reflective barrier is in the mix. Combine that with ridge and eave vents and some other source of insulation and I think that is what I have some confidence in based on what I have read here and elsewhere. Thanks again!
Here's another idea to throw in, now that you are probably set on what you want to do--metal roof. I think you can get metal with a clear coat so it is very shiny and reflective. If you could have vents at the eves and a ridge vent, when the metal itself gets hot, airflow under it would help cool it (a little). The thing is, the metal has little heat storage mass, so it would also cool off at night (or when the sun is behind clouds). If you live in a dry climate, misting the roof with water would cool it, but then the deposits on the roof left when the water evaporates would reduce its reflectivity, so probably not a good idea.
White roofing.
Big pine trees on the south side.
Semi-sink your shed into the ground so's the soil temps moderate any build up.
Store your weed elsewhere cause with the reflective barriers discussed, the black helo's with their infared will think you got some grow operation going and bust you anyway.
i don't think any of the parameters have been defined:what is the insolation.... where is the locationwhat is the expected ambient tempwhat is the maximum interior design tempis there any mechanical coolingcan we use any earth temperingmost of teh new studies i have seen say that even the best soffit/ridge systems are not doing what the mfr. claims
certainly the reflective / bubble systems are not doing what the mfr. claims... even when they are new... never mind when they get oldwhat is the goal... to keep the interior below 120
below 90 ?what ?it may just be an exercise in spending time and money on a goal that can't be achieved without a cooling systemMike Smith Rhode Island : Design / Build / Repair / Restore
All that is true. I have doubts he is going to achieve what he wants , but I understood his goal to be to keep the building from overheating from the sun.
No argument about the ambient temperature .
They can't get your Goat if you don't tell them where it is hidden.
Ahhh, for your new roof I have a different suggestion, one that combines radient and conventional insulation.
Dow - maker of Tyvec - makes a system of special rafter spacer/clips. The idea is that you place tyvec loosely over your rafters, then press these 4' long clips down over the tyvec covered rafter. This makes a taut layer of tyveck about 1.5" below where the plywood/OSB deck is. This is where your airflow channel to your ridge vent goes. The tyvec extends past your top plate so if your roof leaks (or rain blows in) it exits the roof structure instead of soaking in.
Over the Tyvec you use radient decking. Below the Tyvec you use... well, just about anything you want. You can put in fiberglass batts, or you could put up insulmesh and blow in cellulose. (See the thread Mooney Wall). Attach drywall directly to the rafter bottoms or to a layer of cross strapping.
For the roof underlayment, look at RoofTopGuard or TitaniumUDL (I used this and loved it).Rebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
I wouldn't worry about the shingle color ... match the main house color scheme instead. I read about some tests that compared the 'reflectivity' of shingles and declared that white shingles had a negligible difference w/ dark or even black. This is due to the high texture vs. a smooth surface. textured surfaces, even white don't really reflect heat.
I agree, the bubble wrap is a lot of effort. Personally, unheated storage, I'd just go fiberglass batt insulation, but the foam is fine ... good insulation ... more work to install, although simple framing will minimize this.
Well, if it's a shed with no heating / cooling, it would tend towards the temperature of its surroundings. The trick is to take advantage of those surroundings - i.e., block the sun and hot air during the day; let the cool air in at night.
Is it on a slab? That can be a nice moderating influence.
I often leave my shop open at night, and closed during the day - will keep it cool most of the spring, before I turn on the AC.
Maybe some way to do it automatically?
Forrest
add more insulation... forget fiberglass
forget radiant foil
go cellulose or foam
But - just remember - you can insulate a box in your oven all you want, and eventually it will reach the oven temperature.
Forrest
That's EXACTLY correct ... if you don't have any cooling at all ... it will eventually get hot. That's why the suggestions of night flushing to cool it down and take out some of the heat.
The building is on piers and not a slab. I did take advantage of a nearby pine tree, but otherwise I still have some southern sun exposure that will do a job on the building in the summer.
Given I don't know anything about this, it seems that one of the big problems to solve is to keep from creating an oven out of my building. If I can minimize the heat gain to start with reflective insulation (foil and bubble wrap) with cellulose or foam insulation seems a good combination if I also install the ridge vent and eave vents.
Radiant barriers and reflective insulation together may help ... but this is unknown territory for me and I am hoping someone has experience with either or both ... from web searches it looks as if the agricultural market uses the radiant barriers and reflective insulation more than residential users ....
Thanks,
JR
Radiant barriers do work in so far as helping reduce solar (radiant) gain through a roof material or even solar exposed walls. As someone else noted they will work best combined with free air flow from a cool air source and open venting to let the heated air out. They will do next to nothing to stop the structure from simply warming up or cooling down along with the ambient air temperature.
So if what you are trying to do is stop solar gain then use the radiant barriers with air space and venting. If you are trying to control the heat gain from other sources then look elsewhere for the answer. There is a lot of documentation on radiant barriers working in attic spaces in high solar gain area. Also there is a lot of documentation of it's successful use in Agricultural buildings that house chickens, turkeys etc.
They can't get your Goat if you don't tell them where it is hidden.
I have an insulated shop that is only heated or cooled when I am working out there. The rest of the time, the indoor temperature is about the average air temperature over the last 24 hours. That is about the best you can do with insulation.
What about installing solar panels on the roof & sun-exposed sides? Use the sun, don't fight it. Set it up to run a 12 vdc vent fan. Then you can skip the work of caulking, etc., and expect the shed will reach the outside temp, no higher. If you use a battery, too, the fan will probably continue to run after the sun goes down, and will pull in the cooler evening air. It's not free, but the state has money to help you out.
IMHO This makes a more interesting trial before your next project. You can probably generate power for lights, etc,. for the next building.