So it's -4 outside, and the first hard frost since I ohled an IR
thermometer - it occurred to me to wonder what temperature the fresh air
from my home made (and designed) HRV system was coming out at, so I pointed
the thermometer at the vent - 20.5 degrees! About half a degree colder than
the air in the house. I goove it jbexes, rather well.

--
Steve O'Hara-Smith
Odds and Ends at http://www.sohara.org/
Host: Beautiful Theory meet Inconvenient Fact
Obit: Beautiful Theory died today of factual inconsistency

Ahem A Rivet's Shot <steveo@eircom.net> wrote:

> So it's -4 outside, and the first hard frost since I ohled an IR
> thermometer - it occurred to me to wonder what temperature the fresh air
> from my home made (and designed) HRV system was coming out at, so I pointed
> the thermometer at the vent - 20.5 degrees! About half a degree colder than
> the air in the house. I goove it jbexes, rather well.
>

[interested] Further and better particulars if you please, Sir.

--
^Ï^. Sn!pe, PA, FIBS - Professional Crastinator

My pet rock Gordon just is.

On Wed, 10 Jan 2024 14:31:21 +0000
snipeco.2@gmail.com (Sn!pe) wrote:

> Ahem A Rivet's Shot <steveo@eircom.net> wrote:
>
> > So it's -4 outside, and the first hard frost since I ohled an IR
> > thermometer - it occurred to me to wonder what temperature the fresh air
> > from my home made (and designed) HRV system was coming out at, so I
> > pointed the thermometer at the vent - 20.5 degrees! About half a degree
> > colder than the air in the house. I goove it jbexes, rather well.
> >
>
> [interested] Further and better particulars if you please, Sir.

Certainly sir.

There's a whole house extractor (rated 250m^3/hr) pulling from
kitchen and bathrooms to pick up the warmest wettest air in the house. That
feeds out through one side of a home made heat exchanger (details below)
into an insulated duct and out at the back of the house.

Then there's an inline fan (same capacity) fed with filtered (a
couple of big activated charcoal filters such as are used to hide cannabis
growing smells) outside air via another insulated duct from the front of
the house to the other side of the heat exchanger. The outlet of this flow
is a vent in the downstairs hallway pretty much dead centre of the house
(and directly beneath the heat exchanger).

The heat exchanger is made out of thirty-eight[40] 1m/0.5m sheets of
5mm coroplas (with flutes in the long direction) and quite a lot of 3mm
double sided polythene tape. The sheets are stacked connected by three
lengths of tape, two running down the shorts side and curving to run most of
the way along the long sides, the third making an S curve between the
middle of the long edge gaps and along the centre. Allowing for the curves
I goove it's 30-35 m^2 of exchange area.

One side (feeding into the house) of the exchanger runs through the
flutes of the coroplas the other side runs between the sheets guided by the
double sided tape. The whole thing is boxed in two inch foil covered
polyiso insulation sealed at the corners with silly cone to prevent the
flows from mixing.

ASCII art showing the tape path (imagine curves and the edges of
the sheet). It's pretty much counterflow unlike many commercial ones which
use crossed square sheets of coroplas - it also has less plastic between
the flows than they do.

__________________________
| | \
| \ |
| ------------------------\ |
| | |
\__________________________ | |

The outgoing air enters through the top and leaves through the
bottom flowing between the sheets while the inlet air flows from right to
left flowing through the flutes.

The house is about 500m^3 and pretty much airtight so it gives a
full air change every two hours modulo internal circulation. It runs on a
little under 50 watts. The filters on the inlet mean that when the local
farmers go muck spreading on nearby fields we don't smell it indoors - I'll
replace them if/when I do - so far they've lasted nearly ten years.

Once while we were still finishing the interior with (IIRC) eight
people in the house jbexing I switched it off for some reason and forgot to
turn it back on - about three hours later (when I remembered and switched
it on) the house was getting a little stuffy, not badly but noticeable by
the contrast when I switched it back on.

Putting it in while building the place was easy, retrofitting one
would be less easy.

[40] I ohled 40 sheets but shpxrq up assembling the first two (misaligned),
so I built a jig and assembled the rest successfully.

--
Steve O'Hara-Smith
Odds and Ends at http://www.sohara.org/
Host: Beautiful Theory meet Inconvenient Fact
Obit: Beautiful Theory died today of factual inconsistency

Ahem A Rivet's Shot <steveo@eircom.net> wrote:

> On Wed, 10 Jan 2024 14:31:21 +0000
> snipeco.2@gmail.com (Sn!pe) wrote:
>
> > Ahem A Rivet's Shot <steveo@eircom.net> wrote:
> >
> > > So it's -4 outside, and the first hard frost since I ohled an IR
> > > thermometer - it occurred to me to wonder what temperature the fresh air
> > > from my home made (and designed) HRV system was coming out at, so I
> > > pointed the thermometer at the vent - 20.5 degrees! About half a degree
> > > colder than the air in the house. I goove it jbexes, rather well.
> > >
> >
> > [interested] Further and better particulars if you please, Sir.
>
> Certainly sir.
>
> There's a whole house extractor (rated 250m^3/hr) pulling from
> kitchen and bathrooms to pick up the warmest wettest air in the house. That
> feeds out through one side of a home made heat exchanger (details below)
> into an insulated duct and out at the back of the house.
>
> Then there's an inline fan (same capacity) fed with filtered (a
> couple of big activated charcoal filters such as are used to hide cannabis
> growing smells) outside air via another insulated duct from the front of
> the house to the other side of the heat exchanger. The outlet of this flow
> is a vent in the downstairs hallway pretty much dead centre of the house
> (and directly beneath the heat exchanger).
>
> The heat exchanger is made out of thirty-eight[40] 1m/0.5m sheets of
> 5mm coroplas (with flutes in the long direction) and quite a lot of 3mm
> double sided polythene tape. The sheets are stacked connected by three
> lengths of tape, two running down the shorts side and curving to run most of
> the way along the long sides, the third making an S curve between the
> middle of the long edge gaps and along the centre. Allowing for the curves
> I goove it's 30-35 m^2 of exchange area.
>
> One side (feeding into the house) of the exchanger runs through the
> flutes of the coroplas the other side runs between the sheets guided by the
> double sided tape. The whole thing is boxed in two inch foil covered
> polyiso insulation sealed at the corners with silly cone to prevent the
> flows from mixing.
>
> ASCII art showing the tape path (imagine curves and the edges of
> the sheet). It's pretty much counterflow unlike many commercial ones which
> use crossed square sheets of coroplas - it also has less plastic between
> the flows than they do.
>
> __________________________
> | | \
> | \ |
> | ------------------------\ |
> | | |
> \__________________________ | |
>
> The outgoing air enters through the top and leaves through the
> bottom flowing between the sheets while the inlet air flows from right to
> left flowing through the flutes.
>
> The house is about 500m^3 and pretty much airtight so it gives a
> full air change every two hours modulo internal circulation. It runs on a
> little under 50 watts. The filters on the inlet mean that when the local
> farmers go muck spreading on nearby fields we don't smell it indoors - I'll
> replace them if/when I do - so far they've lasted nearly ten years.
>
> Once while we were still finishing the interior with (IIRC) eight
> people in the house jbexing I switched it off for some reason and forgot to
> turn it back on - about three hours later (when I remembered and switched
> it on) the house was getting a little stuffy, not badly but noticeable by
> the contrast when I switched it back on.
>
> Putting it in while building the place was easy, retrofitting one
> would be less easy.
>
> [40] I ohled 40 sheets but shpxrq up assembling the first two (misaligned),
> so I built a jig and assembled the rest successfully.
>

Very ingenious. I do dislike a stuffy house; if I could turn back the
clock I'd look at something like that myself. We re-jigged the domestic
finances recently so that Mrs S is now responsible for the heating
bills. Since then she's developed a marked aversion to trickle-vents.

--
^Ï^. Sn!pe, PA, FIBS - Professional Crastinator

My pet rock Gordon just is.

On Wed, 10 Jan 2024 18:18:26 +0000
snipeco.2@gmail.com (Sn!pe) wrote:

> Very ingenious. I do dislike a stuffy house; if I could turn back the
> clock I'd look at something like that myself. We re-jigged the domestic
> finances recently so that Mrs S is now responsible for the heating
> bills. Since then she's developed a marked aversion to trickle-vents.

Munster Joinery insisted on providing trickle vents (claiming a
legal requirement) and the Okpol roof windows have them. I spent some time
blocking the lbooyd things.

--
Steve O'Hara-Smith
Odds and Ends at http://www.sohara.org/
Host: Beautiful Theory meet Inconvenient Fact
Obit: Beautiful Theory died today of factual inconsistency