ventilation - dcv or alternative?

depadz

Hello,

Am currently doing a refurb of a 1950's house including external insulation.

Have not budgeted for ventilation system other than hole in the wall.

Are the DCV systems recommended? I have been quoted approx. 4K for a complete system supplied & installed.

Are there more cost effective solutions out there?

I do have an architect but would be interested in other opinions.

Thanks..

BryanF

What air-tightness level has been written into the contract?

depadz

none specified in contract.

BryanF

So what is the air-tightness strategy?

Calahonda52

depadz wrote: »

...
Are the DCV systems recommended? I have been quoted approx. 4K for a complete system supplied & installed.

Are there more cost effective solutions out there?

..

What exactly do you mean by a complete system?

Assuming, perhaps incorrectly, that this just does extract from the bathrooms and the kitchen, whats the plan for replacing that air?

For us to help you you need to help us with more information.

What attracted you or the architect to DCV?

What do you mean by more cost effective: cheaper yes, 50 euro crap fans in bathrooms and maybe splurge on a 100 euro crap extractor fan in the kitchen.
So cheaper, but effective, no, so whats the target which is implicit in the A/T question already asked.

BryanF

Calahonda52 wrote: »

What exactly do you mean by a complete system?

Assuming, perhaps incorrectly, that this just does extract from the bathrooms and the kitchen, whats the plan for replacing that air?

For us to help you you need to help us with more information.

What attracted you or the architect to DCV?

What do you mean by more cost effective: cheaper yes, 50 euro crap fans in bathrooms and maybe splurge on a 100 euro crap extractor fan in the kitchen.
So cheaper, but effective, no, so whats the target which is implicit in the A/T question already asked.

We could assume that 4K is a grouped/ducted central mech extract from wc's & kitchen and single wall regulated intake fans in the habitable rooms. And we could assume that 'installed' means designed, commissioned & certified to comply with part F http://www.environ.ie/sites/default/files/migrated-files/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf

depadz

Calahonda52 wrote: »

What exactly do you mean by a complete system?

Assuming, perhaps incorrectly, that this just does extract from the bathrooms and the kitchen, whats the plan for replacing that air?

For us to help you you need to help us with more information.

What attracted you or the architect to DCV?

What do you mean by more cost effective: cheaper yes, 50 euro crap fans in bathrooms and maybe splurge on a 100 euro crap extractor fan in the kitchen.
So cheaper, but effective, no, so whats the target which is implicit in the A/T question already asked.

Its an aereco/lindab system. Exhausts in the wet rooms and wall vents in the rest. My understanding is that the exhaust fans will cause a slight pressure drop in the rest of the house to draw air in through the wall vents. They are constantly open at a trickle & then open more when detect increased moisture/c02 in the air.

The architect has turned out to be a disappointment - is a bit old school as it were. I have an engineer who I find very good.

Whilst have not budgeted for this, I will consider if it is appropriate - but I have other things I can spend 4K on too if it is not a good fit.

I'm not sure about a strategy but new extension is being built to regulations but the old walls of the house are being left as is and will not be at the same standard.

Calahonda52

So cold air is being constantly drawn into the house via the trickle option on the wet room fans and warm air is being constantly ejected.

Does it also require larger gaps under/over doors?

IMhO, I think its a crazy idea, regardless of the price.

I am old school, maybe older school than your architect, but I just don't get the idea of constantly drawing cold damp air into a house.

So how many fans do you get for 4k?

Are the wall vents just dumb wall vents

BryanF wrote: »

We could assume that 4K is a grouped/ducted central mech extract from wc's & kitchen and single wall regulated intake fans in the habitable rooms. And we could assume that 'installed' means designed, commissioned & certified to comply with part F http://www.environ.ie/sites/default/files/migrated-files/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf

Maybe we can but I want to know what is driving the requirement from the client side and how he arrived at this option as opposed to any other option.

It may well comply as you describe but may not be the most cost-effective compliance route

BryanF

Calahonda52 wrote: »

Maybe we can but I want to know what is driving the requirement from the client side and how he arrived at this option as opposed to any other option.

It may well comply as you describe but may not be the most cost-effective compliance route

No info on the air-tightness as yet..

MicktheMan

Calahonda52 wrote: »

I am old school, maybe older school than your architect, but I just don't get the idea of constantly drawing cold damp air into a house.

The air drawn into the house through the vents, while cold, is not damp due to its lower temperature (or at least not damper than the air being extracted). This, afterall, is the whole point of ventilation imo.
For example, extracted air at 20 degC and 70% RH will contain approx 12 grams of water per kg of air whereas air at 5 degC and 90% RH will have roughly 6 g/kg.

murphaph

We're installing an Aereco dcv system in our new build here in Germany. I'm a firm believer in the idea but because it works by forming a vacuum in the house airtightness is absolutely crucial or air will enter the building through any old gap rather than through the passive vents, which is the key to the system. If air can bypass the inlets through random gaps in the fabric, the system is a failure.

Calahonda52

MicktheMan wrote: »

The air drawn into the house through the vents, while cold, is not damp due to its lower temperature (or at least not damper than the air being extracted). This, afterall, is the whole point of ventilation imo.
For example, extracted air at 20 degC and 70% RH will contain approx 12 grams of water per kg of air whereas air at 5 degC and 90% RH will have roughly 6 g/kg.

Agreed, however you, better than most here, will know that we have a more damp/humid environment here than our continental neighbours: it is only relatively recently that continental building materials suppliers have finally bought into that.

In the same vein as you know from another thread there are issue with full MHVR systems in the warm humid conditions we had recently: something I was not aware of so, old school or not, the learning continues.

Calahonda52

murphaph wrote: »

We're installing an Aereco dcv system in our new build here in Germany. I'm a firm believer in the idea but because it works by forming a vacuum in the house airtightness is absolutely crucial or air will enter the building through any old gap rather than through the passive vents, which is the key to the system. If air can bypass the inlets through random gaps in the fabric, the system is a failure.

Are the passive vents just passive vents: i.e. just holes in the wall?

MicktheMan

Calahonda52 wrote: »

Agreed, however you, better than most here, will know that we have a more damp/humid environment here than our continental neighbours: it is only relatively recently that continental building materials suppliers have finally bought into that.

Notwithstanding this, during the heating season, the extracted air will nearly always be wetter than the external air supplied, albeit not to the same extent as on the continental mainland. And therefore, getting the ventilation system / strategy right is actually more critical in our climate than on the continent (and probably why there are so many properties in Ireland with associated problems such as condensation, mould, health issues) and why the lack of understanding of the subject in the industry is worrisome.

Calahonda52 wrote: »

In the same vein as you know from another thread there are issue with full MHVR systems in the warm humid conditions we had recently: something I was not aware of so, old school or not, the learning continues.

Learning should never stop:D

MicktheMan

murphaph wrote: »

If air can bypass the inlets through random gaps in the fabric, the system is a failure.

Agreed.

MicktheMan

Calahonda52 wrote: »

Are the passive vents just passive vents: i.e. just holes in the wall?

They are valves in the hole in the wall which are opened/ closed automatically by the humidity level in the room. The extract fan is a constant pressure fan and reacts to the vents opening / closing using the air pressure, therefore the need for good airtightness.

murphaph

Calahonda52 wrote: »

Are the passive vents just passive vents: i.e. just holes in the wall?

No. They're passive insofar as they require now power. They contain a treated strip of nylon that contracts or relaxes (can't remember which now) when exposed to moisture present in the ambient air. This contraction is used to mechanically open the vent wider to allow more fresh air in when the ambient air is moisture laden. Moisture laden air is a good indicator of occupancy of a room and the air quality is likely to be poor when the air is moisture rich.

Edit sorry didn't see Mick's reply