How do you get on with it? We have to make a decision for our project and I’m struggling to see the benefit; we will be living in the cleanest part of Britain and we always leave windows open so fresh air will enter the house naturally. To us, not opening your windows is unthinkable and the only reason I can see for not opening them is if you live somewhere very noisy or with mosquitos or where the climate is so unpleasant that you want to create your own indoor climate. With a heat recovery system you will have a small electricity cost and extra construction costs as well as the possibility of noise from the fan and I’m guessing you have to clean a filter from time to time, which would have the benefit of removing some airborne dust from the house. Without a heat-recovery system you can have standard extractors in bathrooms and kitchen as you dont have to worry about upsetting the airflow in the system.

Any thoughts?

we will be living in the cleanest part of Britain and we always leave windows open so fresh air will enter the house naturally.

Rural Scotland? It might sometimes enter a little more forcefully than you’d like.

or with mosquitos

Or midges?

Two good points….

I have one. It is noisy, but our house has a wooden frame, wooden floors and no carpet, so a different construction and fittings may absorb some of that sound. It isn’t as noisy as the forced air heating. The noise of the fan doesn’t really come through the vents and is only very apparent in the room beside the utility room.

One thing I have noticed is that all the ducting can be a conduit for outside noise. Thinking occasional barking dogs, rather than traffic.

For us it is essential in the winter to prevent moisture build up in a well insulated building as it is too cold to open the windows. I imagine in a warmer climate it would be more efficient than opening the windows for some fresh air. I have no idea how this would translate financially.

it is great for clearing the moisture from a bathroom. Though it isn’t an HVAC I think it dries the air coming in if the inside air is warmer. Personally, this would be a great benefit living in a damp climate.

Thinking about it, i imagine that the positioning of the vents will create better air circulation than you’d get from opening the windows.

Hope that is of use.

Edit: it is much better than opening the windows to get fresh air in to the house.

More useful stuff, thanks…

We had it in our last place.

It was fairly useless and when it broke (which it did a lot) it made little or no differenced to our bills, and therefore energy usage.

My riding mate runs the Uk distributors for Nilan, the systems are amazing but the houses do need to be built properly for them to work properly so they get involved in the planning stage right the way through to completion. The energy consumption is very low and barely costs him anything to run his system.

https://www.nilan.dk/en-gb/frontpage/dealers/europe

Home

Give him a call and he will be able to talk you though it, and will most likely want to go for a ride when he comes to se you if you say you are into mtb.

Yes, I installed one in the barn whilst under construction. Retrofit would be awkward.

I bought an Itho unit from https://www.cvcdirect.co.uk/ and also got the ductwork from them. Very knowledgeable on the phone and great help in planning.

We use ours through the winter months when external ventilation is generally closed. It works brilliantly. It extracts smells from the kitchen promptly, dries the bathroom after steamy showers and in doing so recovers a good deal of warmth. The house feels fresh and the air is always clean and dry.

I wash the filters a couple of times a year and it’s clear how hard they work. You can tell when the filters are getting full as you can hear the fan labouring a little. Generally the sound is v v low. Only wen I run the fan on boost (10minute momentary timer, with a remote control in the bathroom) to clear the steam from the bathroom can you really here the main fan unit running.

Were I to build another house, it goes on the list of things I would do again.

What pressure test rating have you got to meet for your sap calcs? If it’s super airtight then there will be need for mechanical ventilation and the heat recovery part of it will go towards helping you achieve your figures.
With very airtight properties you can get damp areas without mechanical ventilation.

One of the reasons I installed mine initially was to avoid having to put ugly trickle vents (part F?) in my nice new solid wood windows. No idea of pressures, and there’s no way a barn conversion is airtight, but it is noticeable when it’s working which is good enough for me.

I’m not sure how conversions fair stoner regarding the sap calc side of things. I’m only commenting using my limited knowledge of what we’ve had to on new commercial and the odd housing site we do. With the commercial it’s sbem calcs which I believe is the same as sap, still have to pressure test etc. We go to the nth degree figures wise when say the pressure test doesn’t give us the results we need, so we retrieve data even for the led lights etc to “make the calc work”.
It’s all a bit hit and miss because you do your pressure test once your building is complete and you’re a bit **** then improving it wise.

The house will be timber frame and as per standard practice the whole lot wrapped up in all kinds of membrane, with good quality doors and windows so the architect reckons we will achive a very high level of air-tightness.

We will be having a wood burner and good extraction in the cooking area of the open-plan kitchen-diner, so how does the system cope with the debit when the stove or kitchen extractor are sucking air out of the house?

Your stove may need to have an external air feed to help with draw.

Be very aware that what your architect reckons/designs and what you achieve are two very different things. You need to be very very clear to whoever is doing the build that air tightness is an area that needs to be carefully monitored. I would suggest timber frame houses aren’t all that air tight due to the breathable element of the outer membranes but I may be wrong. Your architect may be relying on the plaster work finish for air tightness so even things such as light fittings where the cables project through the ceiling need to be sealed with clear silicone prior to the fitting going up.

Be very aware that what your architect reckons/designs and what you achieve are two very different things.

I’ve lost count of the times i’ve had this conversation……

Architect: “…. but that’s what’s on the drawing”

Me: “You can do a drawing of a man carrying an elephant. Doesn’t make it a practical solution”

We self built our ultra low energy house just over 3 years ago.

HRV works well for us – the house always feels fresh, there’s no need for heated towel rails – we just have a c60cm rail to drape each towel over and they’re dry even if you’re showering morning and evening. You can dry washing on an airer inside all year without worrrying about damp. I’ve never seen condensation in the house (after the initial drying out period).

Noise – almost in-noticeable. We get more noise from the water circulating in our underfloor heating surprisingingly. Our unit isnt next to any room we sit or sleep in so that needs to be a consideration. Far less noise from outside that there would be through trickle vents.

Caveats
– they not a cooling system. In summer you open the windows. Even in winter you may sometimes want to quickly ventilate a room by opening a window (Scandinavian style). I’ve heard of the idea of this as an alternative ventilation strategy but it doesn’t work so well in the UK because we get cold damp weather rather than the cold dry weather northern continental Europe gets.

– you’ll only get the heat efficiency benefits if the house is properly airtight. UK building regs only require 10 air changes per hour. Passive house is 0.7 (i think we achieved about 1.5 or so). Air tightness requires a lot of effort and detail in construction – almost no UK builders understand whats required. We did it all ourselves, put a lot of effort in and still fell some way short of passivehouse standard…. It needs detailing at every single material junction, window and thoughts about type of fixing and materials used. Some construction methods are better than others – the best I’ve seen used i-joists clad in OSB board on the outside and sealed with a paste down the joins. Much easier to get good results than internal membranes and tapes (which is what we did).

Wood burner and traditional extract will unbalance the system (unless sealed/recirc)

– wood burner. Do you *really* want or need this? Insualation even at building regs standard and you wont need it. Insulate well beyond that (which you should do) and you definitely dont. Not controllable, not airtight, not environmentally friendly. The people i know who have them in efficient houses never use them (my uncle insisted on his fire and we sit there at in mid winter dehydrating in t-shirts).

Cooker hood – extract to outside is a problem – you dont really want any holes in the building. You can get some that extract into the MVHR system but the other alternative is a recirulation hood and a normal vent in the room – that keeps grease out of the MVHR system. Best recirc hoods i found (and fitted) are https://www.berbel.uk Easy to clean out fat and have a very large carbon unit to remove smells (so only needs replacing every few years rather than every 6 months or less with the small cartridge ones)

It works really well – we dont have any issues with grease, smells or moisture in the kitchen. Hood has a link to the MVHR to set it to ‘boost’. Also have humidity sensors in the bathrooms (and on unit itself) so boosts automatically when needed.

almost no UK builders understand whats required

Thanks for the blanket stereotype of “almost all builders”.
Thankfully this one does hence raising the point initially. But as I said it comes back to your architect when specifying products who needs to know his stuff, that point being further backed up by perchy.

We once built a standard 100/100/100 house out of block which was then rendered. It achieved the best results the pressure test guys had ever seen. It’s all about attention to detail.

Peachy – I’d Say you’re the exception that proves the rule. There are some specialists but IME (and from what i see) most UK building is still done to the minimum that standard that can be got past the inspector. Most builds I cycle past in London are still brick and block with the minimum allowable insulation badly installed in the cavity. I struggle to see how they even get to building regs air permeability.

Our house was a SIP frame from a company that sold itself on performance but the guys they subcontracted the frame assembly to were shit.

All very useful information thanks. Having read all that I’m coming round fast to the idea!

On the wood burner, I’m afraid I’m married to the world’s coldest woman and for her, a cosy fire is an essential part of the hygge. Even now in our normal block house we sit with the stove blasting out heat, the TRV on the double rad cranked right open, she shivering and complaining about drafts and I sweating with a knotted hankie on my head and a cocktail with a little umbrella in it… you get the picture. She simply cannot believe that a modern properly insulated house won’t need a stove, so there will be no choice in the matter. Oh and she also wants an AGA!

Aga in a modern house a *really* bad idea. Until you’ve lived somewhere warm and airtight its really hard to understand just how shit the houses most of us live in are.

Maybe try to rent or visit some high energy spec modern homes before you lock down the spec of yours.

Uncle fitted an electric aga (an Everhot?) but they took it out after a few years due to overheating and high costs of running it.

If you want an indication of what this really means our gas bill for heating the house (rather that hot water) is about £250 a year for a 214m2 house. Our neighbours built to an even higher standard than us – they heat their house with a couple of plug in electric radiators (they’ve solar panels and the although straight electric radiant heating is more expensive than gas you’ve save thousands on the hardware and installation of heating system).