Heat recovery system in new build - where's the vents?

Gregor Samsa

Looking at buying a house. It's a one-off brand new build (still being finished). Estate agent listing has it down as A1 BER, and mentions in the bullet points of features that it has a "heat recovery system" and is "airtight" (no other specific information given).

I have viewed the house and didn't think to ask at the time, but looking back over things this weekend, I've realised that I didn't see any vents for the heat recovery system in the ceilings or walls. And there's none in any of the photos or the virtual tour on the listing.

Obviously I can (and will) check this with the EA, but just to satisfy my curiosity before then - should I be seeing obvious vents if there really is a heat recovery system in place? Or could they be hidden in some way? House is at builder's finish at the moment, so there isn't anything in it (including skirting boards) to hide things.

The house does have a hear pump system with underfloor hearing, and the windows do have trickle vents, and I've verified these in person and in the photos. But I just don't know enough about heat recovery systems to know what I'm looking for, and I didn't get to inspect the attic (where I assume the guts of a heat recovery system would be).

Mickeroo

Having trickle vents would point to there being no neat recovery ventilation imo. Would be very unusual and pointless to have both I would have thought

Gregor Samsa

https://www.boards.ie/discussion/comment/121784361#Comment_121784361

Thanks for this. I’m trying to get my head around the various components of a modern house.

Another thing I’ve noticed is that the BER number in the house listing isn’t recognised on the SEAI site. So it sounds like the estate agent has a few things to clarify.

One bathroom has a duct and wiring for an extractor fan in the wall (no fan fitted), but the other two don’t have any. And there’s no provision for an extractor fan vent in the kitchen.

When I first read that there was a heat recovery system, I assumed that this provided the relevant air exchange in these rooms, but now I’m not sure what’s going on.

ColemanY2K

That house doesn't sound very airtight if it's got trickle vents in the windows and an extractor in the bathroom. I'd certainly question it's A1 status and ask the EA what score (ACH = air changes per hour) the preliminary air tightness test came in at. Anything over 3 and I'd run a mile. FYI ...5 ACH is the bare minimum to meet the regs but that is far from optimal.

The MVHR unit could be just what you've seen in the bathroom. You can get single room units that pass through the wall. See here 👇

https://www.ventilationland.co.uk/en_GB/p/decentrale-wtw-unit-o100-mm-met-schakelaar/17954/?gad_source=1&gclid=CjwKCAiA8sauBhB3EiwAruTRJsyuV3Qmx9L13dafz9IH9eCfLJ-7b3jy9sCTZOhz6UHzqpZq6JIz0BoC5SMQAvD_BwE

Calahonda52

Have you seen the A1 BER Cert for a house with trickle vents.

I am a BER assessor so have my doubts

Also these systems need sign off now so ask for that

EA's play fast and loose with this stuff as nothing on their websites is binding

Gregor Samsa

https://www.boards.ie/discussion/comment/121784850#Comment_121784850

No, I haven't seen the certificate. I went to look it up using the BER cert number provided in the listing, but the SEAI website says "no results found". The listing makes a really big deal about the A1 rating, but I'm getting suspicions now. I'll be talking to the EA tomorrow.

It has a 22 panel PV solar array with 5kWh battery, and a heat pump. Could these "technically" push it to an A1 rating without an MVHR system?

Calahonda52

https://www.boards.ie/discussion/comment/121785000#Comment_121785000

Yes they could, which is an issue for me as substituting ESB elec with PV elec to get a better rating does not reflect the true fabric related energy performance.

However, we are where we are.

Ps just read your first post, house not finished means its desktop New build BER, which won't be accessible on the SEAI site

Gregor Samsa

https://www.boards.ie/discussion/comment/121785028#Comment_121785028

Thanks very much.

By "desktop New build BER", does this mean that no site visit was required, and the rating is merely assumed based on the specifications of the build and equipment? Does a "final" BER assessment then need to be done before sale? Or is the desktop one enough to fulfil the requirements?

I'm beginning to see how all this works now. The listing says the house has an energy performance indicator of "-14.97 kWh/m2/yr". I assume that minus figure is a result of being "self sufficient" for electricity via the solar, which lets it away with other energy efficiencies to still rate it ≤ 25 to achieve A1.

ColemanY2K

A PV array that size will without doubt significantly alter the BER calculation.

Biker1

https://www.boards.ie/discussion/2058336742/heat-recovery-system-in-new-build-wheres-the-vents

Someone is trying to pull a fast one. Looks like natural ventilation was specified but an airtightness test result of between 3 and 5m3/hr/m2 at 50pa would have to be achieved in order to allow for this. If so then trickle vents in the windows would fall far short of the requirements for background ventilation. There would need to be rather large permanently open vents in each habitable room. We call this the Swiss Cheese effect as, depending on the size of the rooms there could be a number of vents in each one.

The 22 PV panels are just there to bring the rating down and will do nothing to negate the heat loss via the vents and poor airtightness.

thomas 123

There should be at least one vent in the ceiling in every room.

furthermore there should 2 vents on the wall outside or on the roof in the tiles.

listermint

I've seen centralised ventilation described as heat recovery (wrongly). There there is wall vents not very obvious in the side of bay window or trickle vents for supply. And the 'centralised' extract being in wet room ceilings fed back to the unit on the attic.

This is not heat recovery but some chancers will say it is. It also obviously isn't very airtight.

Gregor Samsa

https://www.boards.ie/discussion/comment/121785286#Comment_121785286

There’s no permanently open vents in any room, except for one bathroom. Other than that, from what I can see, it’s just the trickle vents on each openable window. Which makes me worried about ventilating the kitchen and the other two bathrooms.

Hopefully I’ll get answers on the alleged heat recovery system and the air tightness claims from the EA tomorrow, but he’s been sketchy when we requested other information about other aspects of the build.

Gregor Samsa

https://www.boards.ie/discussion/comment/121785307#Comment_121785307

Now, that's interesting. Because while there's no vents in the ceilings that I can see, there is two holes beside each other in the wall at the attic level.

I wonder were they intended to be for a MVHR system that wasn't installed in the end?

listermint

https://www.boards.ie/discussion/comment/121785440#Comment_121785440

These perhaps would be for supply and extract. But they should be hooded to prevent water ingress from showers.

ColemanY2K

https://www.boards.ie/discussion/comment/121785497#Comment_121785497

..

thomas 123

https://www.boards.ie/discussion/comment/121785440#Comment_121785440

So, if the MHVR was never fitted but it’s airtight walk away.

Will be full of mold if you start living in it. Retro fitting the system would cost a fortune and rip the place apart.

Gregor Samsa

https://www.boards.ie/discussion/comment/121785571#Comment_121785571

Hard to tell from the photos, but from some other reference info I have, I'd say they're about a metre apart.

Gregor Samsa

https://www.boards.ie/discussion/comment/121785621#Comment_121785621

The EA's response will be interesting. We would have found out about all this if we got to the point of having a surveyor checking the place, but it's good that I'm beginning to put a picture together that might help us make decisions before we potentially get to that.

ColemanY2K

https://www.boards.ie/discussion/comment/121785640#Comment_121785640

I have edited my post as I was certain the regs stipulated a minimum of 1.5m but it turns out that was my suppliers minimum recommended distance.

Padre_Pio

https://www.boards.ie/discussion/comment/121785621#Comment_121785621

Not necessarily. The upstairs would be easy with ceiling access from the attic.

The downstairs would be a challenge, but you could get smart depending on the layout of the house and maybe open up only one or two stud walls to run piping to the downstairs ceiling.

For instance, my living room, downstairs bathroom and utility share a wall. It would definitely be a few thousand

ColemanY2K

https://www.boards.ie/discussion/comment/121785766#Comment_121785766

Would you really want to do this to a brand new house you just paid xxx for?

Gregor Samsa

https://www.boards.ie/discussion/comment/121785766#Comment_121785766

There’s no stud walls, and the upstairs floor is concrete.

Padre_Pio

https://www.boards.ie/discussion/comment/121785782#Comment_121785782

Oh definitely not. And I missed the concrete floor comment. Prices just went up!

thomas 123

https://www.boards.ie/discussion/comment/121785766#Comment_121785766

Not exactly the experience you’d want in a home purchase that says it’s included.

I’d also be cautious considering buying a property where such a critical system was omitted for some unknown reason.

listermint

As with everything in life, money talks. Survey properly , but money is key.

keno-daytrader

Trickle vents in a modern house claiming to be airtight? This screams huge winter energy bills to me. What else will they be pulling a fast one on? Insulation..... I would be very concerned that they will be loose with the truth as to what's actually buried in the walls and floor.

No vents in every room = no MVHR.

A1 Ber is horseshite because of the massive boost of a 22 panel PV system.

Mellor

https://www.boards.ie/discussion/comment/121786172#Comment_121786172

the 22 panel PV array is a huge factor in driving the A1 rating. But I'm not sure why people it's horseshite. A PV array generating massive amount of energy does lower the need for external energy. The fact its not balanced over the year is irrelevant.

If nets energy use numbers are accurate, then they that's the energy that is needed. A1 means low net energy neds, it does not means not passive or self sufficient.

listermint

https://www.boards.ie/discussion/comment/121786668#Comment_121786668

BER ratings are mostly shite because people assume high ratings mean warm comfortable home. When the system doesn't really account for that well. Low energy is a cop out if your brand new house is cold and uncomfortable.

Shoog

Retrofitting a 3 bed house with MVHR would cost a minimum of 3k in materials alone. I have heard that translates to around 8k if you get it fitted. If the house price reflects the lack of the MVHR then that not unreasonable additional cost. However the presence of trickle vents means the house can never meet the airtightness requirements of a MVHR system as the vents can never be effectively sealed without taping them closed.

listermint

https://www.boards.ie/discussion/comment/121786853#Comment_121786853

You would remediate existing ventilation like all mhrv installs. Unless you think mhrv is only ever installed in brand new airtight builds?