MVHR woes in Meath

jchardo

Can anyone recommend a MVHR installer who would service the Meath area?

We are building a 2400 sq ft house and are at the roofing stage of the build. We had an MVHR installer but their price has increased from 8000 euro to 12000 euro because of a change in spec (recommended by Zehnder) from manifold system using 75mm ducting to 90mm ducting for use with a Zehnder 550 unit. Needless to say we're disappointed and are currently looking at a change of installer and/or system. Any recommendations would be appreciated.

ptogher14

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Curious Geroge

jchardo wrote: »

Can anyone recommend a MVHR installer who would service the Meath area?

We are building a 2400 sq ft house and are at the roofing stage of the build. We had an MVHR installer but their price has increased from 8000 euro to 12000 euro because of a change in spec (recommended by Zehnder) from manifold system using 75mm ducting to 90mm ducting for use with a Zehnder 550 unit. Needless to say we're disappointed and are currently looking at a change of installer and/or system. Any recommendations would be appreciated.

Can I ask who made the recommendation to go from a 75mm to a 90mm ? We're installing the 550 unit and the installer has used 75mm radial semi rigid all within the envelope of the house.

893bet

jchardo wrote: »

Can anyone recommend a MVHR installer who would service the Meath area?

We are building a 2400 sq ft house and are at the roofing stage of the build. We had an MVHR installer but their price has increased from 8000 euro to 12000 euro because of a change in spec (recommended by Zehnder) from manifold system using 75mm ducting to 90mm ducting for use with a Zehnder 550 unit. Needless to say we're disappointed and are currently looking at a change of installer and/or system. Any recommendations would be appreciated.

I suspect I can guess who your installer was. They are very dear in general. Can't see why the price would jump by 50% due to a change in duct size.

Most MVHR suppliers work nationwide and are happy to travel long distances so perhaps widen your search. I am in Limerick and was in contact with suppliers from Kerry, cork, Galway, meath and Dublin.

Edit: I installed a teed off vent axia system. 6300. It's not commissioned yet but I was very happy with the quality of work for the first fox by the installers. High attention to detail as far as I could see.

Calahonda52

jchardo wrote: »

Can anyone recommend a MVHR installer who would service the Meath area?

We are building a 2400 sq ft house and are at the roofing stage of the build. We had an MVHR installer but their price has increased from 8000 euro to 12000 euro because of a change in spec (recommended by Zehnder) from manifold system using 75mm ducting to 90mm ducting for use with a Zehnder 550 unit. Needless to say we're disappointed and are currently looking at a change of installer and/or system. Any recommendations would be appreciated.

Whats the math on the requirements?
The design starts with extract

that weapon is a passiv haus approved and also designed for an enthalpy option, this all adds to the price
http://www.zehnder.co.uk/comfosystems/index.php?pageID=products_lueftungsgeraet&product_detail:oid=58&template=18_product_detail.html
the weapon has a max flow of 550m3/h

level 2 has the following profile % of max, m3/h, delta P and watts
(6) Level 2 70% 330 215 160

delta P of 215 is a fair whack which means that your A/T needs to be top notch.

What did the initial A/T test throw up?

jchardo

The strong recommendation to change to 90mm ducting came through Zehnder. The reason for the recommendation is because of a concern about noise (especially if the unit is on boost). The installer maintains that noise will not be an issue with the 75mm ducting with the exhausts that he uses and I believe he's being genuine. I would not have a problem pushing ahead with the 75mm ducting but the problem is that the system has to be certified by our M&E and he is very dubious about certifying a system that is not installed as recommended. The price to upgrade to the 90mm ducting has decreased from 12000 to 10000 euro but we were already over budget for the system at 8000 euro.

The total volume of the building is 615m3. We're only roofing at the minute so not A/T test yet.

893bet

jchardo wrote: »

The strong recommendation to change to 90mm ducting came through Zehnder. The reason for the recommendation is because of a concern about noise (especially if the unit is on boost). The installer maintains that noise will not be an issue with the 75mm ducting with the exhausts that he uses and I believe he's being genuine. I would not have a problem pushing ahead with the 75mm ducting but the problem is that the system has to be certified by our M&E and he is very dubious about certifying a system that is not installed as recommended. The price to upgrade to the 90mm ducting has decreased from 12000 to 10000 euro but we were already over budget for the system at 8000 euro.

The total volume of the building is 615m3. We're only roofing at the minute so not A/T test yet.

So they went from 8k to 12k to 10k?

Id cut them loose entirely. Given the labour I'd assume wouldn't have changed due to the duct change the materials increased by 4k and then scaled by another 2k.

Are they trying to find out if they can get the very max out of you?

mp31

Are these worth a look: http://www.viking-house.ie/fine-wire-hrv.html

Calahonda52

You need to see the math here: as I said it designed on extract to begin with and then there are 3 other tests
Extract air flows typically are as follows
Bath room 40
Utility 20
Ensuite 20
Kitchen 60
toilets 20
etc

so say u get to 210 m3/hr

Then there is a Part F fresh air occupancy test, normally taken as 30 m3/h so say 5 people 150 m3/h so 210 still ahead.
Then there is a Part F test of 0.3L/s/m2 by the treated floor area TFA, this is done by whole of house or by room if some rooms are big.
Say the TFA is 242 m2, then the 210 becomes 261

The final test then is for minimum air changes per hr of 0.3, using a max height of 2.5m with the TFA
so 0.3 by 2.5 by 242 becomes 181, plus a 30% boost number becomes 236, so the 261 is the numbe29 m2 area for the ducts to/from unitr
{can't rem where this is from, maybe someone can tell us}

Anyway lets run with the 261
You then need to pick a design air flow rate: say 2.5m/s and there are 3600 second in a hour

261/2.5/3600 gives 0.029 m2 for the area of the ducts to/from unit which is a 300 by 100 rectangular duct or 200mm internal diameter duct.
same way kitchen requires 60m3/h extract, so at 2.5m2/s velocity
60/2.5/3600 gives a duct of c 92mm internal diameter.

ps, is you guy using enough silencers, they need to be on both extract and supply