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OT: Cooling your home with roof space / loft / attic ventilation.

E

Eeyore

Jan 1, 1970
0
I recall some of the US contributors here mentioning a way to help keep the
house cool by actively ventilating the roof space.

With my room temp here upstairs at the sunny front of the house currently @
26.3C and outside air temp @ 25.4C (touched 30 yesterday) I'd like to do
something along these lines to minimise using (with the associated electricity
use) the a/c I have now.

Can you point me in the direction of the stuff that's sold over your way to do
this please ? I can't find anything in the UK but it would help if I knew what I
was looking for !

Graham
 
G

GregS

Jan 1, 1970
0
I recall some of the US contributors here mentioning a way to help keep the
house cool by actively ventilating the roof space.

With my room temp here upstairs at the sunny front of the house currently @
26.3C and outside air temp @ 25.4C (touched 30 yesterday) I'd like to do
something along these lines to minimise using (with the associated electricity
use) the a/c I have now.

Can you point me in the direction of the stuff that's sold over your way to do
this please ? I can't find anything in the UK but it would help if I knew what
I
was looking for !

If you have attic space, its easy. I have been insulating here and there. I'm even advertising
here and there, but received no payments yet. I was using some aluminum backed polyethelene
foam in the basement, because the foam insulation boards requred drywall protection
due to fire issues. I used fiberglass in back of the stuff for better insulation on one side
of the basement, and two layers of just the foam on the other side. The foam does not absorb
moisture. On layer up against the brick and another layer spaced out about an inch. This
eliminates any IR radiated heat flow. So, I bought some foil sheeting thats preforated for use
in the garge. Under the roof spaced about 5 inches out on the supports, I stapled the foil covering
the entire roof. You feel no radiated heat from the roof unlike what it used to be like.
It even insulates a bit with just the airspace. This tough foil like product is preforated,
and can be used on top of attic insulation to reflect any heat back onto the roof. It
can make a big difference. The Prodex stuff probably has an R value of 1 to 2, but the IR
factor adds a couple more. If used with air gaps, its a lot more. The thin foil I used does
not tear, but is only a barrior except for the preforations.

See my Goldstone page.....
http://zekfrivolous.com/goldstone/

greg
 
N

Noway2

Jan 1, 1970
0
Eeyore said:
I recall some of the US contributors here mentioning a way to help keep the
house cool by actively ventilating the roof space.

With my room temp here upstairs at the sunny front of the house currently @
26.3C and outside air temp @ 25.4C (touched 30 yesterday) I'd like to do
something along these lines to minimise using (with the associated electricity
use) the a/c I have now.

Can you point me in the direction of the stuff that's sold over your way to do
this please ? I can't find anything in the UK but it would help if I knew what I
was looking for !

Graham
You are correct about ventilating the roof as having become a standard
practice in the US. This was done as an upgrade in my first house,
which was about 80 years old, and as part of the new construction of my
current house.

There are a few different options available that you could implement (or
not). These include: a roof vent at the peek of the roof, which
consists of a form of membrane that lets the air out, but is water tight
and has a peak shield as part of the assembly, active fans that are
thermostat controlled that will force the hot air out, and roof vents
that are simply weather proof covers that you can put in the roof,
similar to the fans but not as effective. My parents installed one of
the thermostat controlled fans and noticed a definite cooling effect int
heir house.

Another factor to consider is that for proper cooling, you will need to
get air into the attic space. This is done with a form of baffle that
goes in the eaves to allow an air gap between the roof and the
insulation. In older houses, it is also usually necessary to cut an
opening in the eaves as they are more than likely solid. Newer siding,
mostly vinyl, allows for the air flow.

In any case, you will also want to make sure that you install proper
flashing to prevent water leaks.
 
S

Spehro Pefhany

Jan 1, 1970
0
I recall some of the US contributors here mentioning a way to help keep the
house cool by actively ventilating the roof space.

With my room temp here upstairs at the sunny front of the house currently @
26.3C and outside air temp @ 25.4C (touched 30 yesterday) I'd like to do
something along these lines to minimise using (with the associated electricity
use) the a/c I have now.

Can you point me in the direction of the stuff that's sold over your way to do
this please ? I can't find anything in the UK but it would help if I knew what I
was looking for !

Graham

There are electric ventilation fans with a built-in thermostat that
turns them on above a certain temperature. Don't know the brands
offhand.


Best regards,
Spehro Pefhany
 
P

Paul Hovnanian P.E.

Jan 1, 1970
0
Spehro said:
There are electric ventilation fans with a built-in thermostat that
turns them on above a certain temperature. Don't know the brands
offhand.

I have put a few of these in for friends and relatives. They start at
about $50 US each for the horizontal axis models intended to mount
behind a gable vent.

Some years ago, I stuck a thermocouple in my attic, connected to a data
recorder. On a sunny day in Seattle, with 75 °F outside, the attic could
reach 130 °F. Even a good layer of insulation will only slow that down
from heating up the living space.
 
D

default

Jan 1, 1970
0
I recall some of the US contributors here mentioning a way to help keep the
house cool by actively ventilating the roof space.

With my room temp here upstairs at the sunny front of the house currently @
26.3C and outside air temp @ 25.4C (touched 30 yesterday) I'd like to do
something along these lines to minimise using (with the associated electricity
use) the a/c I have now.

Can you point me in the direction of the stuff that's sold over your way to do
this please ? I can't find anything in the UK but it would help if I knew what I
was looking for !

Graham

New construction in my area uses a continuous perforated soffit along
with a continuous roof peak vent (leaves an opening of ~2" along the
whole of the peak. Strictly passive, effective, quiet and maintenance
free.

My house is older and has vents in the sides at the peak, but no
soffit openings. Front and rear have inset doorways and I cut 2' X 4'
holes in them and mounted some SS grills that came out of an
industrial plant air intake. That lowered the heat 25 to 30 degrees F
in summer.

My wife went for a pair wind powered turbine vents on one roof slope.
She has no soffit vents and it is not significantly cooler with just
the turbines - needs a way for fresh air to get in - the vents only
exhaust air.
 
J

John Ferrell

Jan 1, 1970
0
There are electric ventilation fans with a built-in thermostat that
turns them on above a certain temperature. Don't know the brands
offhand.


Best regards,
Spehro Pefhany
Home Improvement stores in the US carry the thermostat controlled fans
for about $50. After the fan motor failed on the one I have in the
garage I replaced the fan assembly with one from a replaced heat
pump. I did not duct it tightly so there is a lot of air circulation
in the attic area.

John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"
 
H

Homer J Simpson

Jan 1, 1970
0
Contrary to popular belief they are not "wind driven", they have very
smooth bearings and the rising heat is enough to turn them, no need
for any wind.

If that were so they would not be needed as they impede airflow. It takes
energy to move them.
 
H

Homer J Simpson

Jan 1, 1970
0
My wife went for a pair wind powered turbine vents on one roof slope.
She has no soffit vents and it is not significantly cooler with just
the turbines - needs a way for fresh air to get in - the vents only
exhaust air.

No icing in winter? With no soffit vents you are asking for ice dams in cold
climates.
 
E

Eeyore

Jan 1, 1970
0

I wondered about that. It makes sense.
If that were so they would not be needed as they impede airflow. It takes
energy to move them.

A little.

The important thing is that they keep the rain and birds out. A hole in the roof
doesn't.

Graham
 
D

David L. Jones

Jan 1, 1970
0
If that were so they would not be needed as they impede airflow. It takes
energy to move them.

Yes it does, and the energy comes from the rising heat.
Wind does help in the efficiency, but is not required for them to
rotate.
They are needed because they are more efficient than a simple hole in
your roof (due to vortex's and such) even with the extra energy
required to drive them, while at the same time keeping out rain.
I've seen simulation models of the airflows and some designs are very
advanced in this respect, much research has gone into them.

Dave.
 
D

default

Jan 1, 1970
0
No icing in winter? With no soffit vents you are asking for ice dams in cold
climates.
Global warming? This past two years we haven't had real frost. Ice
in winter? She has 4 chords of wood that are 10 years old.

Used to be; the ground froze two feet deep in winter, and one spent a
lot of quality time snuggling with the wife - we still open the
windows and turn on the fans but it ain't the same somehow. I still
want the wife and snuggling.

But shouldn't complain - no mosquitoes, "no see ems" and it is late
May.

Perhaps if this continues for a few more years we can grow tomatoes
here.
 
R

Rich Grise

Jan 1, 1970
0
I wondered about that. It makes sense.


A little.

The important thing is that they keep the rain and birds out. A hole in the roof
doesn't.

But when the wind _does_ blow, they turn into centrifugal turbines -
almost like suction pumps.

Cheers!
Rich
 
E

Eeyore

Jan 1, 1970
0
Rich said:
But when the wind _does_ blow, they turn into centrifugal turbines -
almost like suction pumps.

Do they really ? I suppose they might do that

Graham
 
E

Eeyore

Jan 1, 1970
0
Homer said:
in message


Yes, and that's the real point.

So it's better to have electrically powered fans that only run when you need
them then ?

Graham
 
G

GregS

Jan 1, 1970
0
Search for attic fan, or PAV, or powered attic ventilator, or whole house
fan.

See http://www.hometownannapolis.com/cgi-bin/read/2005/06_11-03/HOM for some
comments.

I just installed another attic fan when I had the airconditioner installed
in my new, old house. They are very handy for getting fresh air in and
getting cooling when you don't have to use the air. I even use it to help
clean the house. I turn the fan on high and get out my gasoline air
blower and shower the house. I see cat hairs everywhere. The problem with attic fans,
most I have seen are cheap and don't have much control of the speed. High sounds
like a turbine. I install Green Plugs on them to slow them down a bit.

greg
 
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