Hob extractor in a passivehaus? (or nearly, at least)

[Great_scot_selfbuild]

So we’re going for a very airtight performance timber frame, and visited a nearby build who built to passivehaus spec etc. This was their second self-build and one of the comments they wish they had done differently was route the hob extractor directly outside rather than use a recirculating one, as when it’s operating the noise is noticeable and an annoyance.

 

This may be because they’re comparing it to their previous self-build which went straight outside and wasn’t noticeable inside when operating; it could be that the recirculating extractor isn’t actually that loud. However, we’re in the position where it’s not too late to decide to send the extract air directly outside.

 

We like the idea of it running almost silently, but how do we maintain the airtightness when it’s not operating?

 

Anyone done this? Thoughts?

[Nick Laslett]

I did this. Damper controlled extract vent connected to the extractor hood. Not a fan of recirculating hoods.

 

 

Nothing in the passive house standard says you can’t extract to the outside, but you must factor that into your design. 
 

https://passiv.de/downloads/05_extractor_hoods_guideline.pdf

 

I don’t like noisy, inefficient cooker hoods, so this was an opportunity to try and rectify this with a better solution. Premium cooker extracts are not cheap. 
 

For most on the forum here recirculating hoods work fine. You can fit a filter on the kitchen extract. 
 

 

[JohnMo]

We did recirculation, but we hardly ever use it. MVHR does the job 99% of the time. If we have a few pots boiling, I may put MVHR on to boost, but that's a couple of times a year. 

 

Good hob extractors aren't cheap. If you go recirculating the charcoal filters need to be the regeneration type.

[Tetrarch]

We have recirculation with a Neff Downdraft.

 

The MVHR was designed with this in mind and there's a double extract almost directly over the hood - we've not used the boost

Regards

Tet

[JohnMo]

2 hours ago, Tetrarch said:

double extract almost directly over the hood

Designing that could be problematic in the long term as grease is carried upwards and if you are not careful and have suitable grease filters at the terminals your ducts could be coated in grease then dust etc... 

 

We purposely did the exact opposite, our extract is the other side of the room, about 4m from the hob. We always have a G3 or G4 cone filter in the terminal, it mops up any grease that may get there and any dust anyway 

[Oz07]

I went the hillbilly route and bought a webber bbq. I'm outside in whatever weather doing all the smokey/greasy cooking. Try to keep inside just for boiling things and non greasy stuff

[MikeSharp01]

1 hour ago, JohnMo said:

We always have a G3 or G4 cone filter in the terminal, it mops up any grease that may get there and any dust anyway 

I thought about this approach but decided I wanted the grease in replaceable filter in the MVHR and not more thinly spread everywhere so we have an MVHR extract vent with a grease sock directly above the hob.

[JohnMo]

45 minutes ago, MikeSharp01 said:

I thought about this approach but decided I wanted the grease in replaceable filter in the MVHR and not more thinly spread everywhere so we have an MVHR extract vent with a grease sock directly above the hob.

The cone filter is in the room terminal, so as not to allow anything to get in the ducts. Plus suitable seperation between grease source and extract terminal.

[MikeSharp01]

Our concern was the suitable distance! We were worried that if we did not get close to the source of any particle laden steam / air it would allow said air to get  dispersed and so deposit its load around the place and not into the grease sock - hence we went for directly above the hob. We have yet to commission it all all so won't find out until then