New build MHRV question/ advice

t.kc · 21-01-2019 8:10pm #1

We are nearing the end out our new build and our project manager (a relative) wants to not complete the MHRV ,it is all first fixed and slabbed and plastered but his vuew is leave a few windows open will ventilate the house. I'm concerned as the house has a full airtight membrane, and inner block leaf plastered under insulated slabs. 5inch insulation in cavity. Will the engineer insist on this mhrv being turned on or will the airtightness test stipulate it to be on? My question really is: how do I argue the importance of completing the MHRV and switch ing it on asap.when heating goes live? (Dry out house etc). Cheers.

PS not sure if this is the right forum this

BryanF · 21-01-2019 8:41pm

Is your engineer signing off on building regs?

t.kc · 21-01-2019 10:03pm

BryanF wrote: »

Is your engineer signing off on building regs?

Yes I'd imagine he is, would he not have to?

BryanF · 21-01-2019 10:47pm

t.kc wrote: »

Yes I'd imagine he is, would he not have to?

aren’t the questions your asking best addressed to the engineer?

You need to comply with Building regulations

Ventilation (TGD F) and energy conservation (TGD L)

For drying out the house - open the windows. Be prepared to change mvhr filters every few months for the first year or two due to dust etc.

If your project manager isn’t up to the job and/or familiar with mvhr and air-tightness, perhaps you should send him on a training course or part ways

Mellor · 22-01-2019 6:36am

t.kc wrote: »

We are nearing the end out our new build and our project manager (a relative) wants to not complete the MHRV ,it is all first fixed and slabbed and plastered but his vuew is leave a few windows open will ventilate the house. on or will the airtightness test stipulate it to be on?

MHRV is about energy not ventilation. Which is why opening a window isn't comparable. Also why is "what the PM wants to do" a consideration? Should he not just be following the documentation? Or is there another influence such as trying to achieve a budget?

ht9zni1gs28crp · 22-01-2019 9:28am

t.kc wrote: »

We are nearing the end out our new build and our project manager (a relative) wants to not complete the MHRV ,it is all first fixed and slabbed and plastered but his vuew is leave a few windows open will ventilate the house. I'm concerned as the house has a full airtight membrane, and inner block leaf plastered under insulated slabs. 5inch insulation in cavity. Will the engineer insist on this mhrv being turned on or will the airtightness test stipulate it to be on? My question really is: how do I argue the importance of completing the MHRV and switch ing it on asap.when heating goes live? (Dry out house etc). Cheers.

PS not sure if this is the right forum this

Sounds like somethings been overlooked and to comission the MHRVC may need some backtracking and work removing and refitting. Especially now you say all the plastering has been done....

Just a hunch.....thats all....

Calahonda52 · 22-01-2019 10:33am

miller_63 wrote: »

Sounds like somethings been overlooked and to comission the MHRVC may need some backtracking and work removing and refitting. Especially now you say all the plastering has been done....

Just a hunch.....thats all....

Yep, its a snow job for some cockup

Op go look at what is installed thus far for the MHRV

dusteeroads · 23-01-2019 10:18am

Context matters here.

Do you mean your PM wants not to complete the MVHR for the purposes of drying out the house before occupation ? If so he is correct it is not intended to do that.

The AT test will not look for the MVHR to be fully completed - it is intended to check the building enclosure.

For certifying compliance with building regulations - all systems must be tested and commissioned.

dusteeroads · 23-01-2019 10:19am

Mellor wrote: »

MHRV is about energy not ventilation. Which is why opening a window isn't comparable. Also why is "what the PM wants to do" a consideration? Should he not just be following the documentation? Or is there another influence such as trying to achieve a budget?

The clue is in the name

MV - mechanical ventilation - the primary health and safety purpose of the system

HR - (with) heat recovery - secondary function.

Mellor · 23-01-2019 11:36am

dusteeroads wrote: »
The clue is in the name

MV - mechanical ventilation - the primary health and safety purpose of the system

HR - (with) heat recovery - secondary function.

If you are going to be condescending, make sure you are correvt. :rolleyes:

It's not MV+HR. It's MHRV, the fact you had the rearrage the letters should have been a clue.
The point of MHRV is to reduce the energy lost through ventilation. Energy recovery is the primary function, ventilation is the means by which it achieves that.

Ventilation can be achieved by opening a window (as the PM said), or with fixed windows. You don't need MHRV for ventilation.

BryanF · 23-01-2019 12:37pm

And we’ll leave it there.

dusteeroads · 24-01-2019 10:19am

Mellor wrote: »

If you are going to be condescending, make sure you are correvt. :rolleyes:

It's not MV+HR. It's MHRV, the fact you had the rearrage the letters should have been a clue.
The point of MHRV is to reduce the energy lost through ventilation. Energy recovery is the primary function, ventilation is the means by which it achieves that.

Ventilation can be achieved by opening a window (as the PM said), or with fixed windows. You don't need MHRV for ventilation.

Apologies for my tone Mellor.

I wish to respectfully refer all to TGDF 2009 for the correct terminology - item 1.2.3. and for the intended purpose of the installation item 1.2.3.1

https://www.housing.gov.ie/housing/building-standards/tgd-part-d-materials-and-workmanship/technical-guidance-documents

Mellor · 24-01-2019 11:37am

dusteeroads wrote: »

Apologies for my tone Mellor.

I wish to respectfully refer all to TGDF 2009 for the correct terminology - item 1.2.3. and for the intended purpose of the installation item 1.2.3.1

I'm not sure what your point is. Part F is the Ventilation TGD. It's only focus is ventilation. It also mentions windows - would you argue that a windows primary purpose is ventilation too?

Regarding the order in the acronym. MHRV, MVHR, HRV or being anally accurate MVMHR (that level of specificity is best left to the mechanical engineers imo).
All describe the same equipment. None change the purpose.

Getting back to the OP. The reason his design include heat recovery ventilation, is conservation of energy. So "opening a window" is not an adequate substitute.

dusteeroads · 24-01-2019 2:25pm

Mellor wrote: »

The reason his design include heat recovery ventilation, is conservation of energy.

and you know this how ?

Calahonda52 · 24-01-2019 3:39pm

dusteeroads wrote: »

and you know this how ?

before I add you to my ignore list, let me ask you why else would you pay the extra cost of the heat recovery equipment, including insulated ducting, if it were not for energy saving?

dusteeroads · 24-01-2019 3:53pm

MVHR is marketed as an energy saving measure but that is not it's primary function. TGDL 2011 item 1.4.5.2 also demonstrates this

1.4.5.2 Where a mechanical ventilation
system designed for continuous operation
(with or without heat recovery) is installed for
the provision of ventilation to a dwelling

Note the brackets indicating secondary function.

The reason for installing any kind of mechanical ventilation system is to provide ventilation - especially where to comply with Part L air permeability requirements a Q50 / 5 or better target is met - then one cannot safely rely on non mechanical ventilation.

Scan Part L - where is MHRV - or MVHR mentioned even once ....

BryanF · 24-01-2019 5:42pm

dusteeroads wrote: »

and you know this how ?

Your both arch’s

Let’s agree the mvhr is there as part of a TGD L & F compliance, both for ventilation and energy conversation

dusteeroads · 25-01-2019 10:11am

Agree ? to what end. What light would that shed ?

I will let this be my final post on this thread

https://www.greenbuildingstore.co.uk/information-hub/mvhr-frequently-asked-questions/

Mellor · 25-01-2019 11:23am

dusteeroads wrote: »

Note the brackets indicating secondary function.

Where does that say anything about secondary function, or primary for that matter.

That paragraph is about mechical ventilation. The brackets indicate that. Not all mech is heat recovery. In fact outside of the Irish domestic bubble, most of it isn't.

B-D-P-- · 25-01-2019 11:31am

Lets take a step back, If he's not pulling a fast one to skip MVHR altogether, and just doesnt want to put it on untill the house is finished, I actually agree with him.

Theres so much dust left to be created inside the house from builders from 2nd fixing that the filters would clog.
Open windows are what I did until we were a few weeks from moving and the worst of the dust work was finished.

I started this thread agreeing that it sounded cowboy, but reread the OP, and it sounds like his PM is doing same as me.... BUT also not we are in foggy season, that will do more bad than good when opening windows! I promise you that.

893bet · 25-01-2019 11:35am

You have spent 000’s on Airtightness membranes and plastering behind slabs......now you are going to open windows........

Mellor · 25-01-2019 12:28pm

B-D-P-- wrote: »

Lets take a step back, If he's not pulling a fast one to skip MVHR altogether, and just doesnt want to put it on untill the house is finished, I actually agree with him.

OP says PM doesn't want to not install, not that he doesn't want to turn it on.
I also agree with not turning until most of the dust is removed.

t.kc · 29-01-2019 12:45pm

The pm thinks it's not needed and that opening the windows will suffice. Even with the heating in. Good advice not to turn it in until we are ready to move in for dust reasons .

If it's not turned on I know we would have stale air in the mornings etc. Would there be any other issues/ symptoms?

It's madness spending 000s in airtightness and then not ventilating the house properly I think

newhouse87 · 28-03-2024 10:14am

Just quick bump, noticing good bit of dust around the house, should i up %intake and exhaust speed on my mvhr, its @45% currently. Lad that installed it said i had good airflow around house so could have it lower, that was near 2 years ago.

listermint · 28-03-2024 10:23am

https://www.boards.ie/discussion/comment/121948664#Comment_121948664

The dust is generated from people (you) unless you plan on removing yourself then MHRV won't solve this. It's to reduce outside air contaminants and provide fresh air removing stale air.

You'll just have to up or alter cleaning routine.

newhouse87 · 28-03-2024 10:51am

https://www.boards.ie/discussion/comment/121948698#Comment_121948698

Just thought if i upped speed of fans it would help, i might clean the filters, they are in with 9 months or else ill ask herself to up her game, ill think about that one.

listermint · 28-03-2024 11:00am

https://www.boards.ie/discussion/comment/121948826#Comment_121948826

It won't do much tbh to lift dust off the floors as always though the filters should be changed 6 to 12 months mark.

newhouse87 · 05-04-2024 9:42pm

HAve mvhr throughout the house. Notice when we light stove that we get some stove smells in master bedroom at other end of house.Would this have anything to do with mvhr system?

listermint · 05-04-2024 9:43pm

https://www.boards.ie/discussion/comment/121981948#Comment_121981948

Yes that's a problem. Was it professionally installed and does the stove have its own supply ?

You may have a leak in the stove seals.

newhouse87 · 05-04-2024 9:50pm

we don't get smells even in room with stove so would that rule out stove seals? Mvhr professionally installed.

listermint · 05-04-2024 10:02pm

https://www.boards.ie/discussion/comment/121981995#Comment_121981995

It wouldn't no. The stove should only ever be getting its own air supply and it's exhaust should be out the chimney/flue.

You should never ever have that smell outside the room which means there is supply or exhaust issue or seals are compromised.

newhouse87 · 05-04-2024 10:06pm

Hmm, should I leave air drafts on stove open all the time so when lighting? I tend to close them when fire going well. What do you mean by stove getting its own air supply?

listermint · 05-04-2024 10:16pm

https://www.boards.ie/discussion/comment/121982071#Comment_121982071

Ideal scenario with MHRV is the stove has its own direct air supply. Otherwise it acts as an extract to your mhrv which counters its effectiveness.

This was professionally installed?..

newhouse87 · 05-04-2024 10:23pm

https://www.boards.ie/discussion/comment/121982106#Comment_121982106

Do you mean pipe from back of stove going through blockwall to outside? Yes stove installed by plumber. Stove has double lined flexi going up the flue.

listermint · 05-04-2024 10:26pm

https://www.boards.ie/discussion/comment/121982129#Comment_121982129

Stove should have sealed flue and sealed supply. It's mean to be entirely separate to your home air wise until you open that stove door to load it. Then close it and it's effectively air sealed outside your house envelope.

newhouse87 · 05-04-2024 10:31pm

https://www.boards.ie/discussion/comment/121982135#Comment_121982135

Flue is sealed but air is being drawn up chimney but yeah I assume when I open vents on stove that is house air being used by stove. It's just 1 room that gets the smell though. Rest of house fine just master bedroom has mild smell. May have to get hole in wall so for its own air supply as house airtight.

listermint · 05-04-2024 10:33pm

https://www.boards.ie/discussion/comment/121982151#Comment_121982151

It should have a piped supply to the stove. (Supply)

Your stove is working against your mhrv. Your house is not airtight.

newhouse87 · 05-04-2024 10:39pm

https://www.boards.ie/discussion/comment/121982157#Comment_121982157

All i have is steel pipe with connector from top stove then connected to flexi up flue.Presume turning off mhrv when using stove be stupid idea?

listermint · 05-04-2024 10:52pm

https://www.boards.ie/discussion/comment/121982173#Comment_121982173

I think whomever installed it professionally should have given you advice on how your stove fit into their design.

newhouse87 · 05-04-2024 11:22pm

When putting in stove, noticed we had orange sewer type pipe in ground that leads to outside so suppose won't be too big ofjob to get external supply stove fitted. Builders must have been thinking when plumber and I was not.

Jakey Rolling · 06-04-2024 1:44pm

https://www.boards.ie/discussion/comment/121981948#Comment_121981948

Is the MHRV intake at the same end of the house as the chimney flue?

In certain calm, cold weather conditions we get smoke from chimney not dispersing. I noticed once when going out to the garage, could see the smoke hanging around and drifting down. Stove may have been newly lit so flue not fully heated up.

Our MHRV intake is at far end from chimney so has not been a problem.

newhouse87 · 06-04-2024 1:52pm

https://www.boards.ie/discussion/comment/121984115#Comment_121984115

Its pretty much beside it which seems incredibly stupid.Why I'm thinking of turning off mvhr when lighting stove.

Jakey Rolling · 06-04-2024 1:57pm

https://www.boards.ie/discussion/comment/121982260#Comment_121982260

Is that orange pipe currently sealed at either end? If not, you have a huge breach in your airtightness.

On the other hand, running a regular stove (non room-sealed) with no fixed means of ventilation i.e wall vent in the room could cause CO poisoning. Switching off MHRV with no other source of ventilation would be a bad idea.

At the time we had our room-sealed stove installed the Regs insisted on a fixed vent in the room. May still be the case? The installer had me sign a disclaimer as we had no vent.

06-04-2024 2:00pm

https://www.boards.ie/discussion/comment/109208236#Comment_109208236

MVHR is all about ventilation.

newhouse87 · 06-04-2024 2:01pm

https://www.boards.ie/discussion/comment/121984149#Comment_121984149

No not sealed on outside but stove heart covering it inside. Looks like I'll have to fit new stove next winter so.

newhouse87 · 06-04-2024 3:17pm

https://www.woodheat.org/the-outdoor-air-myth-exposed.html#:~:text=The%20supposed%20benefits%20of%20outdoor,mobile%20homes%20were%20air%20tight.

I seem to have good draught up chimney. I'm thinking the smell is from location of mvhr intake to chimney rather then stove as I have no smell in stove room just v faint in bedroom.

listermint · 06-04-2024 4:53pm

https://www.boards.ie/discussion/comment/121984453#Comment_121984453

Jaysus thats bad that the mhrv feed is close to the stove flue, almost criminal install tbh.

But you should also have had a stove supply installed.. signing a waver seems the install was bad from the get go.

I'd have a serious look at relocating the supply or ditching the stove altogether

06-04-2024 5:03pm

Our MVHR draws in some of the smell of neighbours coal fires and distributed it to all corners of the house. Fortunately it only last for a short while. Fairly much unavoidable to avoid drawing in smells from outside.

newhouse87 · 06-04-2024 5:06pm

https://www.boards.ie/discussion/comment/121984866#Comment_121984866

Didn't sign any waiver. Tbh this is rare I get smells and window open for 2 minutes it's gone so I'm going to leave as is for time being. might make mvhr positive pressure so stove room will have less leakage even though we rarely get smells in that room. Reckon it's just when fire starting is the issue so will turn off mvhr for 30minutes when starting and monitor.

listermint · 06-04-2024 5:10pm

https://www.boards.ie/discussion/comment/121984897#Comment_121984897

Mine doesn't ever.

newhouse87 · 06-04-2024 5:28pm

The intake is good bit below chimney actually so presume that's good.Below as in height. Maybe the thinking is when fire going well smoke will travel farther so better gave it nearer flue.

New build MHRV question/ advice

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