I am planning to install MVHR in my bungalow - 80 sq m on the ground floor and another 40 in what will be the converted loft. I had a quote from 21degrees had previously mentioned Comfoair Q 350 which they said looks like it would be a tight fit but they are also doing a smaller unit called an AIRFI model 100.
When I talked to them last year they mentioned Zehnder.
I can’t see much in way of reviews of Airfi online-- does anyone have any information on their quality and function??
Thank you
Jo
I have personal experience of the same Zehnder unit and can thoroughly recommend it. It is bulky and needs to be installed in the correct orientation, so you can’t juggle the space by rotating it into a horizontal position.
Where is your choice of unit being installed? Most UK retrofits seem to end up in the loft. Mine has. I do have a very large hatch but of course you will have stairs once you get that far.
(I have the Q350 with preheater to prevent the heat exchanger icing up in extreme weather)
The Airfi units are Finnish and have a kitchen bypass, which I found really useful on my previous Norwegian system, however it is not Passivhaus certified. I can’t see a % efficiency but is is EU energy rating A+/A
If you have 1 kitchen and 2 bathrooms then you have a design airflow rate (max)140m3/h max ventilation.
So instinct tell me that a unit that supply 100m3/h which i presume the airfi 100 does. would not be enough?
Obviously you will generally be ventilating at a lower basic ventilation rate that is maybe only half the max. But i would be a little hesitant. Maybe a question you can ask 21 degree? i would be interested to hear their response.
Thanks for that Russell, I will ask them.
Thank you Tim. Originally I was aiming for Enerphit but sadly I just can’t afford it but hope to achieve AECB standard- at least eventually…
What is a kitchen bypass?
It will be in the loft and the plan is for it to go at the gable end but not at the centre as this is where the height is needed for a shower-- so the unit will be in a cupboard,
just did a quick google as i was curious:
The 100 refers to
100dm3/s!!!
which is quite the units!!! this translates to 360m3/h … so you will be more than fine!
But it does beg the question if you only require 140m3/h then there will be slimline products out there, that would be much smaller, so easier to install in your space, and of course significantly cheaper! I guess it depends what products 21 degrees sell.
If they only sell zehder there maybe be somthing like:
Zehnder WHR 920 Basis, but mayube its not available in the Uk.
I too am hoping to achieve EnerPHit one day but it is unlikely. One problem is that I have relatively new non-Passivhaus triple glazing.
A kitchen bypass is linked to a cooker hood and bypasses the heat exchanger. This is necessary for a cooker hood as the air has a high grease level that would damage the heat exchanger.
My cooker hood, from the days of my first MVHR does not have a fan, just a shutoff valve. I haven’t got round to fixing a fan into the duct and finding somewhere to vent it. Family and friends in Norway have similar arrangements. A silent cooker hood is great!
Zehnder do a cooker hood diversion kit, called “ComfoHood”, but it is not available in the UK as it doesn’t meet our building regulations, which possibly means that my self imported^ Norwegian system didn’t and maybe the Airfi one doesn’t unless the kitchen bypass is disabled.
^self imported as MVHR wasn’t readily available in the UK in those days.
Do you have specification for your non PH certified windows?
U values and stuff?
Hopfully you can claw back a bit of heat loss in other ways.
I am a little digruntled at the moment at the certification cost. Especially for DIYers you are really trying their best to make an impact on a budget. Paying for architect sometimes neccisary and a PH consultant is one thing, but then to be slapped with certification.
I am being grumpy but i feel like PH should provide certification for free!!!, based on the fact your buying PH certified products and using certified designers, who all paid. What im trying to say is certification shouldnt be a barrier. i feel it is.
anyway this is a different topic.
My current windows are self declared (always dodgy in my opinion) mid pane 0.8W/(m2⋅K). The frames are 1.0W/(m2⋅K).
As I decorate I am planning on insulating reveals to abut the frames and EWI will eventually abut the outside, thereby reducing frame losses at the window edges but not elsewhere.
21 degress replied by saying;
the AIRFI unit that we would use is called the AIRFI model 100 but its capable of more than 100m3h (more around the 220m3h benchmark for speed 3, which will comfortably cover your property, the 100 refers the model number, unlike the zehnder units which have the maximum flow in their name, which the person on the thread is likely referring to).
Not just Zehnder but other manufacturers include airflow in their product names. It is understandable that using a number not related to airflow causes confusion.
My old Villavent 400R moved 400m3h, so the habit dates back to the start of the century, if not before.
Yeah i think it does refer to airflow, jsut with a different unit as i suggested earlier:
The 100 refers to 100dm3/s!!!
this translates to 360m3/h
But good to get some confirmation
I’m inclined to agree with you Russell. Unless 21° checked with the manufacturer their answer is just as much supposition as anyone else’s. When I lived in Scandinavia there was a lot of use of deci- prefix. Fair enough, it is a deci-mal system. I had to get used to decimeters and decilitres in everyday usage.
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