how RS Components survives

"Ross Herbert" <rherber1@bigpond.net.au> wrote in message
news:idhoa6hmksth3hpm3mo67j8jpfoqvje2es@4ax.com...
Yes, I did do some research into low speed large diameter fans of the type
you
mention http://www.breezepower.com.au/breeze_power_2a4.pdf but they were
fairly
expensive and there was a bit more installation work required. I would
point out
that by installing ceiling vents in all rooms a roof mounted exhaust fan
will do
a similar job to the above unit. However, my main objective is to reduce
the
temperature of the air trapped in the roof space so that it does not
overload
the insulating properties of the ceiling insulation, so I do not plan to
install
ceiling vents initially. I will install a number of vents around the eaves
to
allow the intake of cooler air to the ceiling space. By having only a
single
exhaust hole in the roof for the fan I anticipate that warmer air will not
leak
out too quickly during the cooler months because the fan will never be
turned
on.
Click to expand...
Unless you live in Tasmania, one fan type roof vent is not enough. They are
cheap, and can be easily blocked in winter, (and the blades fixed) which is
what I do.

MrT.
 
On Thu, 7 Oct 2010 11:59:30 +1100, "Mr.T" <MrT@home> wrote:

:
SNIP
:
:Unless you live in Tasmania, one fan type roof vent is not enough. They are
:cheap, and can be easily blocked in winter, (and the blades fixed) which is
:what I do.
:
:MrT.
:
:

It also depends on the volume of air which must be exhanged in a given time in
order for any cooling effect to become meaningful. As you say, a single vent is
far from ideal but I would have thought that a fan driven vent (Powervent) which
is quoted as being capable of exchanging 250L/s would not take too long to
remove and replace the air volume in my roof space. Passive "whirly bird" type
vents don't move that much air and that's why you need 6 - 8 of them to provide
similar proficiency to the fan driven unit. I would certainly like to try to
retro-fit self closing flaps onto the fan when I get it just so the vent stays
closed when it is not required during winter.
 
On 7/10/2010 10:17 PM, terryc wrote:
On Thu, 07 Oct 2010 09:40:15 +0800, Ross Herbert wrote:

It also depends on the volume of air which must be exhanged in a given
time in order for any cooling effect to become meaningful. As you say, a
single vent is far from ideal but I would have thought that a fan driven
vent (Powervent) which is quoted as being capable of exchanging 250L/s
would not take too long to remove and replace the air volume in my roof
space.

My only gotcha with this is where does the "cooler" air come from? when
everything around your hose is 40 deg C, not much point in pulling in air
at the same temperature.
Click to expand...

common practise to pump heat into the ground hence returning cooler
air to the house and very efficient
I would certainly like to try to retro-fit self closing
flaps onto the fan when I get it just so the vent stays closed when it
is not required during winter.

FWIW, There are 12"(?) room vent fans made with self closing flaps.
Click to expand...

--
X-No-Archive: Yes
 
On Thu, 07 Oct 2010 09:40:15 +0800, Ross Herbert wrote:

It also depends on the volume of air which must be exhanged in a given
time in order for any cooling effect to become meaningful. As you say, a
single vent is far from ideal but I would have thought that a fan driven
vent (Powervent) which is quoted as being capable of exchanging 250L/s
would not take too long to remove and replace the air volume in my roof
space.
Click to expand...
My only gotcha with this is where does the "cooler" air come from? when
everything around your hose is 40 deg C, not much point in pulling in air
at the same temperature.

I would certainly like to try to retro-fit self closing
flaps onto the fan when I get it just so the vent stays closed when it
is not required during winter.
Click to expand...
FWIW, There are 12"(?) room vent fans made with self closing flaps.
 
On Thu, 07 Oct 2010 22:31:18 +1000, atec77 wrote:

common practise to pump heat into the ground hence returning cooler
air to the house and very efficient
Click to expand...
I'm really not looking forward to digging the trench for that. I just
wish I'd had thought of it when I put in a network of stormwater drainage
pipes. It would have been so easy to have just droped another run of
drainage pipe into the trench higher up.
 
"Ross Herbert" <rherber1@bigpond.net.au> wrote in message
news:bp8qa693edhid3o424to821dfua83hqpm6@4ax.com...
SNIP
:
:Unless you live in Tasmania, one fan type roof vent is not enough. They
are
:cheap, and can be easily blocked in winter, (and the blades fixed) which
is
:what I do.

It also depends on the volume of air which must be exhanged in a given
time in
order for any cooling effect to become meaningful. As you say, a single
vent is
far from ideal but I would have thought that a fan driven vent (Powervent)
which
is quoted as being capable of exchanging 250L/s would not take too long to
remove and replace the air volume in my roof space. Passive "whirly bird"
type
vents don't move that much air and that's why you need 6 - 8 of them to
provide
similar proficiency to the fan driven unit.
Click to expand...

Yes, it was that type I was referring too, but they are cheap to buy, cost
nothing to run, and require no maintenance. So about four for an average
house is no big problem IMO. Nor is blocking/unblocking them twice a year
IMO. Your powervent will obviously work on a completely still summer day
however.

Most people don't use them simply for the same reason they buy halogen
downlights, they have no clue!

MrT.
 
"terryc" <newsninespam-spam@woa.com.au> wrote in message
news:i8kdp0$ngf$3@speranza.aioe.org...
My only gotcha with this is where does the "cooler" air come from? when
everything around your hose is 40 deg C, not much point in pulling in air
at the same temperature.
Click to expand...

Here's my take on it. Putting in under eaves vents is actually wrong. If you
have cavity walls, air will be drawn up from under the floor which will
definitely be cooler than the air in a non ventilated roof space.

MrT.
 
On Fri, 8 Oct 2010 11:46:32 +1100, "Mr.T" <MrT@home> wrote:

:
:"terryc" <newsninespam-spam@woa.com.au> wrote in message
:news:i8kdp0$ngf$3@speranza.aioe.org...
:> My only gotcha with this is where does the "cooler" air come from? when
:> everything around your hose is 40 deg C, not much point in pulling in air
:> at the same temperature.
:
:
:Here's my take on it. Putting in under eaves vents is actually wrong. If you
:have cavity walls, air will be drawn up from under the floor which will
:definitely be cooler than the air in a non ventilated roof space.
:
:MrT.
:

Thanks for that tip. Since my house is double brick - cavity construction it has
numerous vent bricks low down on the external wall so I will wait to see how it
performs without eave vents.
 
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