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Insulating a roof with no crawl space Kompu Kid 05-06-2008
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Posted by Kompu Kid on May 6, 2008, 8:20 pm
Just bought a home built in 1950. The roof I suspect has minimal
insulation. To make the ceilings high, the builder has put in no crawl
space and the rafters are visible from inside the house.

The house is only around 1000 sq.ft. It is in San Jose California.

I looked at the archives of this usenet group, and found discussions
on using foam blocks under the composite shingles. This seems fine
but it seems like it is like building a new roof, which could be
expensive.

I am thinking of the following alternatives:

- Add foam from within in between the rafters and blend them with the
architecture.
- Erect an awning (maybe I should call this a tent) that will cover
all of the roof for the hot summer months.
- Put solar panels. They would not only make shade put also generate
electricity for me. However, I hear that solar panels and convertors
etc. can be very expensive.
- Or, put a solar water heating system.


How would one insulate such a roof?


Thanks!

Deguza





Posted by ransley on May 8, 2008, 8:29 am
> Just bought a home built in 1950. The roof I suspect has minimal
> insulation. To make the ceilings high, the builder has put in no crawl
> space and the rafters are visible from inside the house.
>
> The house is only around 1000 sq.ft. It is in San Jose California.
>
> I looked at the archives of this usenet group, and found discussions
> on =A0using foam blocks under the composite shingles. This seems fine
> but it seems like it is like building a new roof, which could be
> expensive.
>
> I am thinking of the following alternatives:
>
> - Add foam from within in between the rafters and blend them with the
> architecture.
> - Erect an awning (maybe I should call this a tent) =A0that will cover
> all of the roof for the hot summer months.
> - Put solar panels. They would not only make shade put also generate
> electricity for me. However, I hear that solar panels and convertors
> etc. can be very expensive.
> - Or, put a solar water heating system.
>
> How would one insulate such a roof?
>
> Thanks!
>
> Deguza

Exposed rafters so you actualy see the roof deck or whatever finish
product is attached? Spray foam would be best, there are R 5 and R 7.2
foams, then finish the ceiling. How thick is the open area in inches
to insulate, you want what is appropriate and maximum in R value for
your area.

Posted by PeterD on May 8, 2008, 9:03 am
On Thu, 8 May 2008 05:29:57 -0700 (PDT), ransley

>> Just bought a home built in 1950. The roof I suspect has minimal
>> insulation. To make the ceilings high, the builder has put in no crawl
>> space and the rafters are visible from inside the house.
>>
>> The house is only around 1000 sq.ft. It is in San Jose California.
>>
>> I looked at the archives of this usenet group, and found discussions
>> on  using foam blocks under the composite shingles. This seems fine
>> but it seems like it is like building a new roof, which could be
>> expensive.
>>
>> I am thinking of the following alternatives:
>>
>> - Add foam from within in between the rafters and blend them with the
>> architecture.
>> - Erect an awning (maybe I should call this a tent)  that will cover
>> all of the roof for the hot summer months.
>> - Put solar panels. They would not only make shade put also generate
>> electricity for me. However, I hear that solar panels and convertors
>> etc. can be very expensive.
>> - Or, put a solar water heating system.
>>
>> How would one insulate such a roof?
>>
>> Thanks!
>>
>> Deguza
>
>Exposed rafters so you actualy see the roof deck or whatever finish
>product is attached? Spray foam would be best, there are R 5 and R 7.2
>foams, then finish the ceiling. How thick is the open area in inches
>to insulate, you want what is appropriate and maximum in R value for
>your area.

I wonder if these techniques that have been suggested may be hard on
the roofing shingles (if they are heat sensitive, such as your typical
asphalt shingles)? I know here in New England (not a hot spot) that
roofs that have an insulated deck tend to have much lower shingle life
than roofs which have some ventilation built into them.


Posted by ransley on May 8, 2008, 2:38 pm
> On Thu, 8 May 2008 05:29:57 -0700 (PDT), ransley
>
>
>
>
>
> >> Just bought a home built in 1950. The roof I suspect has minimal
> >> insulation. To make the ceilings high, the builder has put in no crawl
> >> space and the rafters are visible from inside the house.
>
> >> The house is only around 1000 sq.ft. It is in San Jose California.
>
> >> I looked at the archives of this usenet group, and found discussions
> >> on =A0using foam blocks under the composite shingles. This seems fine
> >> but it seems like it is like building a new roof, which could be
> >> expensive.
>
> >> I am thinking of the following alternatives:
>
> >> - Add foam from within in between the rafters and blend them with the
> >> architecture.
> >> - Erect an awning (maybe I should call this a tent) =A0that will cover
> >> all of the roof for the hot summer months.
> >> - Put solar panels. They would not only make shade put also generate
> >> electricity for me. However, I hear that solar panels and convertors
> >> etc. can be very expensive.
> >> - Or, put a solar water heating system.
>
> >> How would one insulate such a roof?
>
> >> Thanks!
>
> >> Deguza
>
> >Exposed rafters so you actualy see the roof deck or whatever finish
> >product is attached? Spray foam would be best, there are R 5 and R 7.2
> >foams, then finish the ceiling. How thick is the open area in inches
> >to insulate, you want what is appropriate and maximum in R value for
> >your area.
>
> I wonder if these techniques that have been suggested may be hard on
> the roofing shingles (if they are heat sensitive, such as your typical
> asphalt shingles)? I know here in New England (not a hot spot) that
> roofs that have an insulated deck tend to have much lower shingle life
> than roofs which have some ventilation built into them.- Hide quoted text =
-
>
> - Show quoted text -

Yes I wasnt thinking, it will have some effect. I dont know what the
procedure is on SIPS construction, if venting is used and how shingles
last. But for metal, slate and tile it would not matter. I dont his
utility costs but they will likely double soon and that may be more
important. Venting could be done by running a spaced sheeting away
from the roof deck, but at what cost, maybe a different type of roof
material would be better.

Posted by Kompu Kid on May 8, 2008, 3:56 pm
>
>
>
>
>
> > Just bought a home built in 1950. The roof I suspect has minimal
> > insulation. To make the ceilings high, the builder has put in no crawl
> > space and the rafters are visible from inside the house.
>
> > The house is only around 1000 sq.ft. It is in San Jose California.
>
> > I looked at the archives of this usenet group, and found discussions
> > on =A0using foam blocks under the composite shingles. This seems fine
> > but it seems like it is like building a new roof, which could be
> > expensive.
>
> > I am thinking of the following alternatives:
>
> > - Add foam from within in between the rafters and blend them with the
> > architecture.
> > - Erect an awning (maybe I should call this a tent) =A0that will cover
> > all of the roof for the hot summer months.
> > - Put solar panels. They would not only make shade put also generate
> > electricity for me. However, I hear that solar panels and convertors
> > etc. can be very expensive.
> > - Or, put a solar water heating system.
>
> > How would one insulate such a roof?
>
> > Thanks!
>
> > Deguza
>
> Exposed rafters so you actualy see the roof deck or whatever finish
> product is attached? Spray foam would be best, there are R 5 and R 7.2
> foams, then finish the ceiling. How thick is the open area in inches
> to insulate, you want what is appropriate and maximum in R value for
> your area.- Hide quoted text -
>
> - Show quoted text -

Yes, I believe that is what I am seeing from within inside the house.
The rafters are at least 6" down from the roof.

I can create with 2x2's cells in between the rafters and put foam
blocks then cover the cells with plywood, then stain them to match the
original ceiling color and the exposed rafters.

I wonder if I can use reflective bubblewrap top of insulation instead
of foam. (Here is what I am talking about: http://www.btubusters.com/attic-c=
eiling-detail.html).
I hear that the R values of these are very good.

Here something similar to my ceiling:

http://www.loghomebuilders.org/files/images/log-home-master-bedroom-cathedra=
l-ceiling-jj35.preview.jpg

In my case rafters run in the other direction and the distance between
the rafters is far greater. That's why I think I would need to create
cells.

If I were to go with cells filled with foam, is there any ventilation
neede between the foam and the ceiling?

Deguza

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