Why do I need a wall vent?

plunkettrebel

We are currently building a 2050 square foot house. We were aiming for between an A2&A3 house. We are goingt o have an externally vented stove and an open fire. I was advised to put a removable cap on the chimney of the open fire. The BER assessor said we will have to a wall vent in the room with the open fire for safety because of carbon monixide. We are going to put in a HRV system and a breathable membrane around the windows.
I can't understand why we are going to spend so much money on getting the house air tight then we'll have a wall vent freezing the house!!!! We're going starting the blocks in 2 weeks time.

frag4

HRV= no vents in my book.

holdfast

Firstly i would get rid of open fire full stop. the only reason you will reach A2/A3 is cause the assessor is using your stove as the secoundary heating. its playing with figures so real "world issue here " the houses perfromance will be affected. 2nd point having a HRV and and open fire and a vent is a big waste of money, put in a second stove with external air supply. The BER assessor is playing silly bugger a little knowledge is a dangerous thing using an open fire place and hrv and then putting a vent ?? the house may be an A3 on paper but it wont perform like one.

plunkettrebel

I asked the assessor about why do we need a vent when the hrv would be working also,he said that we could always close the vent when the fire is not use, but whats the point of having one in the first place???

plunkettrebel

Thanks for that holdfast,I was thinking about fitting an external vented stove built into the fireplace, that should eliminate the need for the vent.

holdfast

No problem, yea a external air supply for both stoves will work best. if you are going to get a HRV make sure it on the SAP index and you aim for 3 air changes an hour for the test for best results.

plunkettrebel

It's on the SAP index alright,I didn't know about the amount of air changes,cheers

sydthebeat

plunkettrebel wrote: »

I asked the assessor about why do we need a vent when the hrv would be working also,he said that we could always close the vent when the fire is not use, but whats the point of having one in the first place???

sack your assessor... he/she hasnt a clue!!!!

firstly if you have an externally air sourced (room sealed) stove then there is not significant effect on your hrv system, carbon monoxide is not an issue as there is a flue vent.... fed from teh external so no air infiltration heat losses.

secondly, any *ahem* assessor that specified a 'hole-in-the-wall' when you are going to teh expense of installing a HRV system clearly does not understand what they are talking about. It calls their scope of knowledge into question.

Have you got an architect or architectural technician involved in this build?? who is specifying they construction elements?? who will be certifying that the build complies with regulations??

RVR

This isn't as clear cut as it seems, because the guidance is a bit lax on this (as with everything else!!!)

I believe the assessor is in the right here. For an open fire you need air supply from the room. If your MVHR unit broke then it could lead to a dangerous situation with CO buildup in the room.

On one of SEI's BER bulletins they point out that

"Permanent air supply
vents associated with the chimney or open flue are not counted in addition to the chimney or open flue"

http://www.sei.ie/Your_Building/BER/BER_FAQ/FAQ_BER/Assessors/April_Technical_Bulletin.pdf

This means you could put your vent for safety purposes but it would not harm your energy rating as it does not have to be entered on DEAP.

PS - of course if you have a room sealed appliance then this would not be necessary and you would never otherwise use vents with MVHR.

seclachi

Every single person I have talked to about HRV says you cannot have a open fire, and it makes sense, the entire house is air tight and then you have this big hole bang in the middle of it all, its like putting air holes in a a submarine.

An airtight stove is probably the way to go. If the room has windows I cant see having no vent being a problem, if the HRV does go down, and you postivily have to use the stove you can just open the window a crack.

Id reccomend a carbon monoxide detector no matter what you go for (Air tight stoves could always malfunction too), if something is pumping out carbon monoxide you dont want an air vent to be your last line of defence.

sydthebeat

RVR wrote: »

For an open fire you need air supply from the room. .

use of a room sealed stove equates to NO chimney or open flue being inputted into DEAP. Thats what the OP is specifying.

guidance being lax should not equate to bad practise.

RVR

You're right about not using a vent with a room sealed appliance, however the OP clearly mentions open fire?!?

plunkettrebel wrote: »

We are goingt o have an externally vented stove and an open fire... The BER assessor said we will have to a wall vent in the room with the open fire

sydthebeat

RVR wrote: »

You're right about not using a vent with a room sealed appliance, however the OP clearly mentions open fire?!?

you are completely correct, i read it wrong (it though it was or an open fire)
my apologies.


to the OP... don't install an open fire... its completely counter productive and a waste of a lot of your money....

RVR

sydthebeat wrote: »

don't install an open fire...

Now there's the best solution!!!

plunkettrebel

I spoke to the BER assessor about the changing the fireplace to incorporate an intergrated external vented stove. He gave me a couple of numbers of heating merchants. The BER assessor said we can include the vent into the chimney by running a pipe up by the flu, so elimanting the need of the wall vent. Asked the builder what would he recommend because we are going to use a foam concrete block. There seems to be a limited range available, just looking on line neither Stanley or Mulberry supply these types of stoves.