C3 Rated Semi-D & Mechanical ventilation system (heat recovery)

ButtUcks

We have a purchased a 4 bed semi-d with a C2 energy rating.

The attic isn't insulated nor are the cavity walls.

So I'm wondering a house, described above (briefly) would benefit with MVHR?

kkelliher

ButtUcks wrote: »

We have a purchased a 4 bed semi-d with a C2 energy rating.

The attic isn't insulated nor are the cavity walls.

So I'm wondering a house, described above (briefly) would benefit with MVHR?

Sorry not a MVHR expert so will allow others assist but I have never being a fan of BER certs calculations and you would wonder how a house with no insulation can achieve a C2 rating

shanered

My guess its a new enough house is it?

ButtUcks

shanered wrote: »

My guess its a new enough house is it?

New-ish - 1990

BryanF

Realistically what is your budget?

Imo
Achieving Mvhr required levels of air-tightness & insulation in an existing building can be distributive and expensive. There are alot of things you'd want upgraded before going with MVHR. I think its a great challenge but I tend to push a simpler RH (realitively humidity) extract system minus the heat recovery element.

You would want to be at 1.5'ish ACH (air change per hour) with triple glazed air-tight windows, and external insulation achieving a continuos .2wm2k insulation. Efficient space & water heating... Etc

sydthebeat

ButtUcks wrote: »

We have a purchased a 4 bed semi-d with a C2 energy rating.

The attic isn't insulated nor are the cavity walls.

So I'm wondering a house, described above (briefly) would benefit with MVHR?

1. theres no way your house is C2 rated and it has NO attic insulation and NO cavity insulation

2. typically, semi -d's were 'production line' built so attention to specific details in each dwelling was not of a high priority

so id suggest
1. clarifying the above insulation issue and if there is actually really no insulation at all, apply for the SEAI better energy homes scheme grant.

2. after this, get an energy consultant to do a blower door test and prepare a report on best way to improve energy efficiency.

ButtUcks

BryanF wrote: »

Realistically what is your budget?

Imo
Achieving Mvhr required levels of air-tightness & insulation in an existing building can be distributive and expensive. There are alot of things you'd want upgraded before going with MVHR. I think its a great challenge but I tend to push a simpler RH (realitively humidity) extract system minus the heat recovery element.

You would want to be at 1.5'ish ACH (air change per hour) with triple glazed air-tight windows, and external insulation achieving a continuos .2wm2k insulation. Efficient space & water heating... Etc

Had a feeling the attic & cavity walls (and whatever else) would need to be insulated first, and this is why I love boards.ie

Thanks for your input & advice re RH venting. I'll have to google that!!

RITwing

sydthebeat wrote: »

1. theres no way your house is C2 rated and it has NO attic insulation and NO cavity insulation

2. typically, semi -d's were 'production line' built so attention to specific details in each dwelling was not of a high priority

so id suggest
1. clarifying the above insulation issue and if there is actually really no insulation at all, apply for the SEAI better energy homes scheme grant.

2. after this, get an energy consultant to do a blower door test and prepare a report on best way to improve energy efficiency.

Agreed. Something is waaaay off here.
Look at the advisory report that by law must be made available to you.
It will make statements about what actions are needed to improve the house

ButtUcks

RITwing wrote: »

Agreed. Something is waaaay off here.
Look at the advisory report that by law must be made available to you.
It will make statements about what actions are needed to improve the house

Will do & thanks.

MOTM

Along with all of the above, particularly Syds post, adding mvhr to a house that isn't fairly well sealed will make your BER and energy usage worse.

You get no benefits from the heat recovery due to the leaky structure and are going to have electric fans running the mvhr.