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Solar Thermal Design For Historic Home - Page 8

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Posted by daestrom on August 20, 2006, 3:14 pm
 


<snip>

I'm surprized no one has suggested more insulation in the attic.  6" seems
pretty little insulation.  I'm used to colder climates and 20" is more
'typical'.  Or is the attic finished off and you only have 6" space to work
with?  If that's the case, I would have gone for foam board or some other
high-performance insulation in that 6" space.

I understand about the walls, you don't want to tear them apart.  But attics
usually aren't too hard.

daestrom
P.S.  Conservation measures almost *always* pay back faster than any other
form of heating/cooling.


Posted by Ed on August 21, 2006, 6:34 am
 
daestrom,

Hmmmm. The Google server seems to be acting up on me, but I'll try and
reply again.

The attic is a walkup attic and the floor (over ceiling joists) has a
subfloor installed that covers the existing 6" of insulation.  I will
eventually put down a finished floor, but that won't provide much
insulation value.

When we re-roofed the house with new standing seam metal roofing
material, we first put down a neopreme type water and ice shield over
the entire roof and that added some (not much) insulation value.

It might be possible to add foam board insulation between the roof
rafters in the attic to improve the overall R-Value up there.  I'd have
to place the insulation boards up against the open sheathing boards
(purloins) and glue the insulation boards to the sheathing boards and
rafters.  Remember, we're talking about a house built in 1891.

I want to be very, very careful that I don't cause the attic to sweat
and build up excess moisture.  By installing insulation boards up
against hot sheathing that has a hot  neopreme shield next to it might
allow infiltrated moist air from the air conditioned living space
below, and outside air, to be trapped against the hot insulation boards
and/or neopreme shield and thereby generate unwanted moisture and
perhaps mold.

When we re-roofed the house I rebuilt the soffets (great fun), but have
not yet installed soffet vents.  I have some additional electrical work
to finish in the attic and want to install a thermostatically
controlled attic fan prior to cutting open and installing the soffet
vents. To date there has been no excess moisture accumulation in the
attic and I'd like to keep it that way.  Certainly, I want to move the
hot air off of the living space ceilings during the summer months, but
I want to be careful about attic moisture accumulation.

This old house is very well built but it does "breathe," which means it
has air exchanges in unusual places.  I prefer not to make it so tight
that it prevents adequate fresh air exchanges.  It has stood for 115
years and all the wood is dry and there is no rot or moisture damage.

Ed

daestrom wrote:


Posted by Ed on August 21, 2006, 6:36 am
 daestrom,

Hmmmm. The Google server seems to be acting up on me, but I'll try and
reply again.

The attic is a walkup attic and the floor (over ceiling joists) has a
subfloor installed that covers the existing 6" of insulation.  I will
eventually put down a finished floor, but that won't provide much
insulation value.

When we re-roofed the house with new standing seam metal roofing
material, we first put down a neopreme type water and ice shield over
the entire roof and that added some (not much) insulation value.

It might be possible to add foam board insulation between the roof
rafters in the attic to improve the overall R-Value up there.  I'd have
to place the insulation boards up against the open sheathing boards
(purloins) and glue the insulation boards to the sheathing boards and
rafters.  Remember, we're talking about a house built in 1891.

I want to be very, very careful that I don't cause the attic to sweat
and build up excess moisture.  By installing insulation boards up
against hot sheathing that has a hot  neopreme shield next to it might
allow infiltrated moist air from the air conditioned living space
below, and outside air, to be trapped against the hot insulation boards
and/or neopreme shield and thereby generate unwanted moisture and
perhaps mold.

When we re-roofed the house I rebuilt the soffets (great fun), but have
not yet installed soffet vents.  I have some additional electrical work
to finish in the attic and want to install a thermostatically
controlled attic fan prior to cutting open and installing the soffet
vents. To date there has been no excess moisture accumulation in the
attic and I'd like to keep it that way.  Certainly, I want to move the
hot air off of the living space ceilings during the summer months, but
I want to be careful about attic moisture accumulation.

This old house is very well built but it does "breathe," which means it
has air exchanges in unusual places.  I prefer not to make it so tight
that it prevents adequate fresh air exchanges.  It has stood for 115
years and all the wood is dry and there is no rot or moisture damage.

Ed

daestrom wrote:


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