My ancient detached shop/garage has an uninsulated roof and now that
temps are parked in the 90's with full sunshine most days, the heat
radiating from the roof turns it into an oven. Things inside (like
projects) get warm to the touch and the ambient temperature soars to
about 105°(40.6°C). I've had to move all glues and solvents and
anything else that might be temperature sensitive into the house. As
you can imagine, it makes things like brushing shellac difficult. Any
ideas for a cheap remedy just for the radiating heat problem? I know I
could insulate the roof, but that isn't the direction I want to go with
this space. Before winter sets in, I want to frame about half of the
inside of the building into a room for the wood shop and insulate that,
but I didn't want to do it now. The building is about a 1000 sq/ft and
the roof is over 12' high at the peak, so that isn't very practical
anyway. I was thinking along the lines of maybe using a reflective
coating for the roof or tacking down tarps to cut down on the heat
absorbing properties of the black shingles. Does this sound practical
In a word, NO! Been there, done that. I had a shed that was hotter
than a firecracker when the sun came out. I painted the roof stark
white and put a thin layer of insulation on the inside of the roof. The
temperature drop was nearly unnoticeable. Years later I tore the shed
down and built my own. fiberglass shingle roof, 2 small gable vents,
thicker insulation AND I insulated the walls that were exposed to the
sun. Now on a HOT, HOT day I can walk into that shed and be greeted by
coolness akin to walking under a large shade tree.
If you don't insulate where the heat load is coming from you can forget
about cooling your shop. Of course the dark roof is much of the
problem, but the larger problem is lack of insulation.
Hax Planx wrote:
I was thinking along the lines of maybe using a reflective
Well I am going to differ from David's view. I live in Houston. Last
year I built a storage room in my back yard with no insulation. I used
Radiant barrier decking for the roof and went with 30# felt and a premium
asphalt shingle on top of that.
The room stays closed up all day long and the inside temperature never feels
higher than the out side temperature. 2 weeks ago I painted the out side a
medium brown color and the inside temperature rose slightly.
While it may not be feasible to re roof your building and put down radiant
barrier decking there is radiant barrier paint that can be sprayed up on the
bottom of the roof. They may help and be relatively inexpensive.
Keep in mind also that insulation does not warm or cool a building it simply
slows the temperature movement going from a warmer area to a cooler area.
If the building does not cool down at night insulation is probably not going
to help. IMHO the trick here is to reflect the heat with the proper
Oddly the radiant barrier products face towards the inside of the building.
the metallic surface on the decking faced down and the radiant barrier paint
is applied on the same surface facing down.
is that room primarily or wholly in the shade, Leon? There isn't any
way to be comfortable in a totally uninsulated outbuilding here during
the summer if the sun beats down on it. White roof, brown roof, purple
roof--makes such a marginal difference if there's no insulation in the
walls/roof. In fact I've got almost the same roof on my shed as on my
house and the house is hotter than the shed because of all the frickin
single pane glass that I've yet to replace. Removing a wide sliding
door (single pane) on the south side of the house and replacing it with
a 36" triple glazed door helped tremendously to keep that end of the
house cooler. YMMV--and apparently it does. <g>
No, not in the shade at all. In fact when I painted it brown it became
slightly warmer. I went with radiant barrier because I wanted to see if it
really worked and it only cost me $24 more than standard decking. I was
really amazed at how much it helped.
It _is_ amazing how proper construction methods can keep temperatures down
inside a structure.
I just walked in from checking the gas furnace line installation in the
attic of a new house built with radiant barrier roof decking and ridge
venting ... it was no hotter in that attic than it is outside today in
As you well appreciate, being in an attic in Houston at 11 AM on a sunny
June day can be a scorching experience in the older houses. AAMOF, the
shingles on this one were already too hot to install the HVAC roof vents ...
I like to have that done at first light, before the sun get overhead, to
keep from damaging the shingles.
Now, if I ever get the time to build that new $hop ...
It is amazing. My wife and I have been looking at new homes and Ryland is
guaranteeing that heating and cooling costs will not be over about $50 per
month on average for a full 3 years. This is on homes ranging in size from
2,000 to 3000 sq feet. IIRC they are using radiant barrier plus that new
blown in wall insulation that is made up of old newspapers like on TOH.
That is the way my store room is. You can almost touch the decking and it
is no warmer.
Where are you planing on putting that new shop? LOL
$50 a month for heating and cooling ??? They must have
figured out a brand new way to heat water for the
laundry or dish washer.
At the VERY cheap rate of .08 per kwh, that works out
to 625 kwh per month for heat or cooling.
I don't think my home would be that low if "nobody"
was living there.
I assume these homes are NOT total electric ???
Laundry and dishwashing are not heating and cooling costs directly.
The $50 sounds very cheap given today's energy, but not impossible in a well
insulated house. I can do 2000 sq. ft. for less than $100
As for the people living there, they add to the total heating, not to the
Body functions = heat
Light bulbs = heat
Computer = heat
Cooking = heat
Washing + drying clothes = heat
I consider any $$$ on that electric bill to be money
out the door. We currently pay over $30 for various
"energy related" extras tacked on to the normal bill.
I suspose they could come up with a cooling number or
a heating number, but the total bill will vary pretty
widely from one area of the country to the next. Our
current rate of .08 kwh is about average for the country.
The impression I got from Leon's message was that the
"total" bill to be $50 per month, which I found unrealistic.
Edwin Pawlowski wrote:
As a P.S. to my comment. My supplier was very insistant that knew to lay
the radiant barrier decking with the foil side down as some of the
installers put it with the foil side up and the roofs only lasted 4 or 5
years. Radiant barrier IIRC does nothing to keep a house from getting cold
in the winter.
I re-roofed my entire house and garage in January. I went back with
radiant barrier and ridge vents AND a BLACK roof! The garage (my shop)
is now cooler than it has ever been. I lower the garage door about
half way in the afternoon to block the afternoon sun. Its the first
time I've been able to tolerate working out there during the day in the
summer. Yes, I need a fan blowing on me, but it used to be unworkable
As you know, I too, live in Houston.
Ah, takes me back to my college physics days. The reason why insulation
and a radiant barrier are needed is because heat can be transferred in
two ways: by physical contact of one substance that is hotter than the
one next to it, or by infrared radiation. Insulation protects against
the first type of heat transfer, but like you said, unless it
incorporates a reflective barrier, which a lot of it does now, it will
absorb infrared along with the rest of the house. This is bad in both
the summer and winter. In the summer, your house, including the
insulation, absorbs infrared from the sun. Then long after the sun goes
down, your house may still be hot and sticky because it has stored all
that energy and continues to radiate it onto you. It is bad in the
winter because when it absorbs the infrared, it eventually must radiate
it away, but the radiation goes in every direction. Some goes back into
your house (good), some is radiated away (bad). When IR hits a
reflective material, it bounces off instead of being absorbed. Infrared
isn't heat, it becomes heat when it is absorbed by some material.
Infrared barriers act the same way a mirror does, which is why they are
bright and shiny. Infrared barriers are good in summer and winter
because in the winter, it reflects the infrared back into your house
heating some object that can absorb it, and in the summer, it reflects
IR from the sun instead of allowing the material under it to absorb the
IR and beam it inside.
I know that's more than anybody wanted to know, but since I spent five
years cramming on this stuff, it should be useful for something.
nope. mass absorbs heat. insulation slows it down.
a heavy brick wall will take longer to heat up than aluminum siding
over frame, but it will hold that heat late into the night. insulation
slows down the transmission of heat. add r80 in the form of fiberglass
of rigid foam or whatever and the inside of the house will stay cooler
longer into the day and cool down earlier in the evening.
Spray isocythene insulation would be a solution. Also something like
the foil/bubble/bubble/foil insulation would be easy to install (just
need a staple gun and the time) and I did that a couple years ago on
a addition (quasi-garage) we built with BOTH the
foil/bubble/bubble/file AND fiberglass bats in the wall studs, and it
is noticeably cooler in there than outside util be open up the garage
doors at both ends, then it equilabrates to the outside temp
I totally agree, without adding insulation/radiant barriers, you are
not going to accomplish any significant temp reductions
On Tue, 28 Jun 2005 15:58:05 GMT, "Leon"
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