HRV with no natural ventilation?

coillsaille

We are currently at the stage of selecting windows (triple glazed) for our new build. The house will be very well insulated and airtight (expected 0.6 ac/h) with a HRV system.

The living/sitting room will be nearly 50sqm with a high vaulted ceiling. This room will have all glazing to the south (20sqm or so) as well as some glazing to the west.

The view to the south is quite impressive and we would like to avoid obstructing it in any way, therefore we were considering one entire glass wall. However the window companies we have talked to say we need to have windows that will open as overheating will be a major issue in the room.
(We can't have openings in the west facing windows due to their design - tall, apex style.)

My question (if anyone knows) is during warm weather would the HRV (in summer bypass mode) be able to stop this room overheating without natural ventilation??
If its of relevance there are two doors into this room, one from the kitchen and one from the entrance hall.

Appreciate opinions on this.

DOCARCH

Check the building regulations! HRV or no HRV you still need opening windows/external doors to all habitable rooms = to 1/20th the floor area of the room.

AFAIK, HRV will not keep a room cool in warm weather.

If you are going for large areas of south facing glazing you should be looking at ways and means to prevent overheating from solar gain by looking at solar shading/overhangs/bride soleil.

coillsaille

DOCARCH wrote: »

Check the building regulations! HRV or no HRV you still need opening windows/external doors to all habitable rooms = to 1/20th the floor area of the room.

AFAIK, HRV will not keep a room cool in warm weather.

If you are going for large areas of south facing glazing you should be looking at ways and means to prevent overheating from solar gain by looking at solar shading/overhangs/bride soleil.

Ok thanks for that.

If building regs come into it then we don't really have a decision to make. I'm pretty clueless when it comes to regs but it was actually my QS who suggested the HRV would be enough to prevent overheating, so I thought he would be aware of regulations.

Just to clarify, I know HRV won't keep the room cool but just trying to find out if it would help at all in reducing overheating.

Good point on the solar shading, that's something to consider.

gman2k

I think you have two options;
1 Design in Shading/ Brise Soleil to remove overheating
2 Turn off HRV when the indoor temp gets too warm and ventilate using windows.

HRV summer bypass doesn't do anything if you ask me.

BryanF

Hi, and the best of luck on your project but

coillsaille wrote: »

We are currently at the stage of selecting windows (triple glazed) for our new build. The house will be very well insulated and airtight (expected 0.6 ac/h) with a HRV system.

if you expect 0.6 ac/h you should have had a study done on solar shading and measures in place (open windows/doors/ shading for potential overheating!)

The living/sitting room will be nearly 50sqm with a high vaulted ceiling. This room will have all glazing to the south (20sqm or so) as well as some glazing to the west.The view to the south is quite impressive and we would like to avoid obstructing it in any way, therefore we were considering one entire glass wall. However the window companies we have talked to say we need to have windows that will open as overheating will be a major issue in the room.

what has your architect/energy assessor got to say ??

(We can't have openings in the west facing windows due to their design - tall, apex style.)

arch ditto

My question (if anyone knows) is during warm weather would the HRV (in summer bypass mode) be able to stop this room overheating without natural ventilation??

we need to see your design, and we need to question your designer..

coillsaille

Thanks for the replies.

if you expect 0.6 ac/h you should have had a study done on solar shading and measures in place (open windows/doors/ shading for potential overheating!)

Yes, we should have, but the overheating issue has only come up for discussion now as we approach the stage of window selection. This is my first (and last!) time being involved in a build, and none of the professionals involved have mentioned it before now. I guess the focus has been on keeping the building warm, by availing of as much solar gain as possible.

But from the opinions given here, and by windows people, I now realise that attention also needs to be given to the possibility of having too much solar input in the building and how to vent it.
It's really only an issue in this one room as all other south-facing rooms have large opening windows or sliding doors.

what has your architect/energy assessor got to say ??

Afraid the architect's involvement is limited to design stage and signing off/certifying as we couldn't afford his services for managing the build.
I do have a very good contractor with experience of low-energy building and a QS on board.

DOCARCH

coillsaille wrote: »

I now realise that attention also needs to be given to the possibility of having too much solar input in the building.

That's it - you've pretty much summed it up. As much attention/thought needs to be given to avoiding the risk of over heating as solar gain - a balancing act. From the sounds of it you could bake yourseleves in your Living Area!

Have you had a preliminary BER done? There are some (limited) inputs in DEAP to do with shading of windows to help avoid overheating.

BryanF

imo give your architect an opportunity to solve the issue

coillsaille

BryanF wrote: »

imo give your architect an opportunity to solve the issue

Taking you and Docarch's opinion into account, added to the fact that I will soon need to decide on a heating system, I think a BER guy is the next port of call.

Not to mention that my architect bills me for every minute of his time spent on this build!