Renegade105

Totally agree

Yes well I said that for dramatic effect but in all honesty open up your MVHR’s and tell me for sure you don’t have any crossing of air streams…especially as the heat enhangers start to build up. do you know how they test to make sure there is no crossing? Do you know if they test as the cells get a bit blocked? Sorry to question it all.. it it’s what I have found out upon questioning myself.

My final input into this thread then. 1) I’m not sure I can comment on if an extractor is even required or not. Apart from building control, I suppose if someone doesn’t even cook, then it’s not a big issue. Each to their own which is fine. 2) finally, MVHR have very coarse filters that leak a lot..they don’t have a HEPA filter so all the harmful PM1 and 0.1 (mainly those 0.1-0.3 microns particles) just get dumped into the rest of your house, so you dilute it within the envelope of the home. As you will likely have an airtight house with a low Air Change per Hour (currently mostly set at around 0.3 ACH, it will take officially around 3.3 Hours for all of those nasties from the 10 mins of cooking to leave your home..and that’s not taking into account mixing and stalling of air currents within rooms. 3) I have a final thought, if I had a petrol generator and fired it up in my house for 1minute a day and had the exhaust go into my MVHR, is that ok? I mean I can turn my generator on outside and leave it running for an hour so what’s the bumig deal if it’s inside and connected to my fancy MVHR?

https://passivehouseplus.ie/magazine/insight/hell-s-kitchen-why-cooking-can-destroy-indoor-air-quality A simple example worth reading.

@ G and J. 😂 that had me in stitches. I’m used to dealing with nuclear dust, asbestos, molecular pollution such as NOx and all within a regulated environment where standards and testing matter hence why I chirped into the discussion. its perfectly normal to get this push pack sometimes as I get it from my builders! Typical comments I’ve had are: what’s the point in an air tight house, buildings need to breathe…ASHP will never work, how will you get hot water…MVHR..well that’s obviously a rich person con…..£100 roll of tape…are you insane….VOC’s….they don’t do anything…PM1 particles, that’s fake…NOx …my diesel is eco…electric cars…total scam…Solar? Never gonna work in this country…Wood fiber insulation…what a con….ICF…I’ve obviously lost it now, triple glazing (show off), and finally the kitchen extractor 😬. list just goes on.

Don’t supply to your plinth, you will get cold toes.

I think usually for the extract vent flaps would suffice however a motorised one would be better. Just a bit more complicated and expensive. for the inlet, check out iris dampers..have a better control of the flow however I have seen that you might need a fan in any case for this make up air circuit. seriously a window might be so much easier if possible. You can even get motorised window openers for max feel levels.

Hi. yes you can do a motorised inlet valve to allow balancing….or open a window?

And finally..carbon filters have a dwell time to work..and that is how carbon filters work. carbon coated media (which is what you can buy) are saturated very quickly,,and they don’t operate in high humidity..something to consider when admiring the steam doing a 180 degree turn.

Consider these points and again base it on what’s important. 1) where in those guidelines does it really discuss IAQ, or even test it..shouldn’t guidelines be based on that? 2) filter lifetime are 1-3 months..so what happens at the end of 1-3 months? Are filters 100% blocked? How would you know if you need to change 1 or 3 months? Would you be happy buying a car with a fuel gauge that says refill at 1-3 months? we need to start questioning the norm guys..it all stinks.

I can do better then that…don’t cook at all that way you don’t have any pollutants. beleive it or not, even induction jobs create pollutants…heat provides the enthalpy change required to create chemical reactions too..just saying. I know this is a bit of a tricky subject, and as I said I am just giving my 2 cents, especially for people who use the kitchen a fair bit.

When deciding on an extractor fan in an airtight house, I think your answer is guided by what your priority is. 1) IAQ- indoor air quality, both particulates, grease and molecular pollution (go for external vent) 2) Heat loss- (go for a recirculating hood) 3) MVHR- Forget about using that to clean up the air, the ones you have can't even deal with a firework display or your neighbours log burner 5 streets away, but that's another topic all together. In my opinion, recirculating fans aren't very effective. Yes as the previous post alluded to, pulling steam might work quite well, great, but water vapour isn't a concern if IAQ is your priority. If you care about removing the particles generating when cooking, then the filter and carbon wont do that as they're too small and too coarse. The worry here is you don't actually see the pollutants coming off when you're cooking, you only see the really large particles that aren't particularly harmful as your cilia and hairs lining your respiratory tract can deal with them. Its the tiny particulates that cross your BBB (blood brain barrier), the ones that easily are absorbed through your lungs that you need to watch for, and you have no chance filtering out the molecular pollution, unfortunately the carbon needs a long contact time to work...a thin bed of carbon wont do. Did you know none of the kitchen extractors are really regulated in any way. Apart from some distance above the hood and some European energy limits on the fan, its pretty much do whatever you like. In the end, I believe your health should come first, that means losing your warmed expensive air and for that you get a slightly colder home but you and your family are hopefully alive for longer to enjoy said cold house for longer. Keep it simple. In my opinion, an extractor hood, and a remote fan away from the user so noise doesn't limit how fast you run it when its required. This means a lot of the time a custom hood, and for that you need quite a large duct too. Remember to wire up a light switch and fan controller near the user in the kitchen, and make the wife promise to open the window if she wants to cook anything. A chef is in the most harmful zone , directly above/in front of the pollutant source, so you have better create a good negative pressure zone there to scavenge away the harmful stuff away from them, just like you would if you were soldering, there's really not much difference. Just my 2cents to anyone considering their new home or refurb.

@happyfolk Hi, ok so the 417 with 100mm vane and a hood is NOT the best at getting reliable readings, far too much error. You need a powered flow hood. Might look the same but totally different. You can hire it if you wish (BSRIA) to do the balancing yourself. Finally, I can’t see where the supply vent is…is it a linear vent which has been plastered in that recess in the ceiling? Can you get access to the cutwork, perhaps there is a mass flow damper upstream of the vent that you could take flow readings with using a manometer. Good luck

Hi dude, Not sure if its too late to ask but why add a screed over the top of the slab? You could tie the UFH pipes into the Slab directly, just ask Tanners and they will sort it? Or it is a very large footprint/area, in which case lie would be a lot easier doing it your way to get a level floor.

My Engineer only specified Rebar over the openings for our ICF build in England too.