Ventilation Regs

[cwhaley]

Hi all, having a small extension built and so far so good. We’re about halfway up to the roof of the single storey build. Just thinking ahead and have been asking about means of ventilation. Building control have said that the new downstairs WC (containing a toilet only) must have means of mechanical air extraction and that an opening window is not sufficient as it’s not safe. I have been reading through Approved Document F and cannot find anything to support this, other than that the ventilation rate must be 6/L and that mechanical or manual means are acceptable (purge ventilation). I'd prefer just the opening/lockable window.


I will also be having a utility room containing a washing machine and condensing tumble dryer. Again we’ve been told we’ll need means of mechanical air extraction this time at a rate of 30/L.


Is anybody clued up enough on document F to help me out here? Don’t want to go back to the BCO quoting things I’ve not quite got right as so far we’ve got on well.

 

[Swwils]

For the purposes of part F, sanitary accomodation is also regarded as a wet room.

A utility room is specifically mentioned.

Purge ventilation is a seperate requirement, for use when there are high concentration of pollutants or water vapour. Like painting or a spillage.

It's not the primary aspect of your ventilation strategy. BCO sounds in the right.

 

[cwhaley]

For the purposes of part F, sanitary accomodation is also regarded as a wet room.

A utility room is specifically mentioned.

Purge ventilation is a seperate requirement, for use when there are high concentration of pollutants or water vapour. Like painting or a spillage.

It's not the primary aspect of your ventilation strategy. BCO sounds in the right.

Thank you. I'm happy for - and understand the need for - the utility room to have mechanical air extraction, given its use.

For the WC (toilet only) however, the planning portal states: "For toilets only, ‘purge ventilation’ (an opening window/door on an external wall) meeting the requirements specified in Appendix 2 of Approved Document F - Ventilation can instead be used to provide ventilation if security is not an issue".

That statement is what's made me want to query the apparent need for another extractor fan. Surely only real concern is to extract odour?

 

[Swwils]

The planning portal is probably just "guidance".

I think approved document used to say "Intermittent extract rates are given in Table 5.1a. For sanitary accommodation only, as an alternative, the purge ventilation provisions (windows) given in Appendix B can be used where security is not an issue" under the table for intermittent extraction. Maybe it does still say this.

All in all it does not sound like a big issue, maybe the BCO has identified something where the fan might be an improvement.

 

[garyo]

Most upvc windows can be locked in a 5mm open position. I thought that this was the purpose of that setting?

 

[cwhaley]

Most upvc windows can be locked in a 5mm open position. I thought that this was the purpose of that setting?

Exactly my thoughts too, but apparently it's "not really accepted anymore" according to BCO, citing security as a reason.

If I have to have an extraction fan I have no choice, but the planning portal seemed to suggest I don't. Plus it does seem incredibly excessive given the room is 1.4m long by 0.8m wide.

 

[^woody^]

The principle is that utility room use will create excessive moisture which can then affect other parts of the house, for longer periods, just like a kitchen or bathroom can. So you need an extract fan or central passive system.

 

[Bouy]

The principle is that utility room use will create excessive moisture which can then affect other parts of the house, for longer periods, just like a kitchen or bathroom can. So you need an extract fan or central passive system.

Yes but why the WC. Is house security part of building regs now?

 

[^woody^]

Yes but why the WC. Is house security part of building regs now?

Part Q.

I didn't read/register the bit about the WC.

Purge ventilation from a window should be sufficient for a WC.

 

[Bouy]

Part Q.

I only asked but thanks anyway

 

[Bouy]

Exactly my thoughts too, but apparently it's "not really accepted anymore" according to BCO, citing security as a reason.

So by that reasoning there shouldn't be any opening windows in any rooms because of security?

 

[clifford1]

So you might have an electrified fence, alsatian guard dogs, alarm link to the police and a night watchman, but if you had a downstairs loo with a window too small to climb through you would still have a security risk?
I didn't realise Building Control had such a wide-ranging remit - when did they become security experts as well?

 

[cwhaley]

Thanks for the replies, all.

As I say totally understand the need in the utility room -- even though there will be no sink or open water, the tumble drier creates enough humidity alone to warrant a decent extractor. It was just the separate WC which threw me as I can't understand the need for one given the use of the room. The reason I don't want one though is that I'm trying to avoid having a bank of vents on the side of the extension because... aesthetics.

The BCO's reasoning for a fan in the WC is "Locking the windows ajar is no longer acceptable at ground floor level due to the security risk". He's due to come tomorrow to see the floor once it's been poured, so I'll give him a call when he's been and have a chat about it. It seems I'm not alone in questioning the need.

 

[RandomGrinch]

I know it's way too late now!
...and this might say something about how my mind works
When I was out today, this thread jumped into my head and I thought 'why not have a window with a vent light, that no-one can fit through!'

 

[cwhaley]

I know it's way too late now!
...and this might say something about how my mind works
When I was out today, this thread jumped into my head and I thought 'why not have a window with a vent light, that no-one can fit through!'

Nah not too late, windows still not gone in yet we got delayed by a late skylight delivery.

Now this probably says a bit about how my mind works, but what's a vent light??

BCO eventually confirmed we don't need an extractor fan in the utility room (as there will be no sink) and the same goes for the downstairs WC. His only real concern was that it doesn't pose a security risk if left open accidently.

From outside the windows will be 8ft in the air (the house is built 2ft off the ground), and they are only something like 488mm x 450mm.