Ventilation

alemap83

Hey,

Currently in the middle of a new build. We are making the house airtight but not going down the road of MHRV as we are putting a solid fuel range in the kitchen. The solid fuel range cannot be connected to an external air supply.

I got a quote for a demand controlled ventilation system but it is very expensive. We were just thinking of putting a few wall vents in. I heard that there is humidity controlled wall vents available.

Would anyone have any recommendation on the best way for us to ventilate our house please? The house is 3000sq ft.

BryanF

What is the expected air-tightness/ ACH (air change per hour) ?

In my experience demand control vent sysytems are half the price of Mvhr systems, they typically work on a RH sensor. You need to do more research, and really question what is motivating the solid fuel range in the kitchen- a gasification log boiler in the garage, small room sealed stove with back boiler, an MVHR sysytem would be a better way to go imho

893bet

alemap83 wrote: »

Hey,

Currently in the middle of a new build. We are making the house airtight but not going down the road of MHRV as we are putting a solid fuel range in the kitchen. The solid fuel range cannot be connected to an external air supply.

I got a quote for a demand controlled ventilation system but it is very expensive. We were just thinking of putting a few wall vents in. I heard that there is humidity controlled wall vents available.

Would anyone have any recommendation on the best way for us to ventilate our house please? The house is 3000sq ft.

You cannot build an airtight home and not put in Mvhr. You will have mould everywhere.
You cannot build an airtight home and put in wall vents (what would be the point)
I am not sure if an airtight house with demand controlled ventilation will meet part L of the regs.

Get rid of the solid fuel range idea. Put in a room sealed stove with dedicated airsupply and mvhr and enjoy the benefits of a low energy home for the rest of your life.

alemap83

The expected ACH is 0.2

893bet

alemap83 wrote: »

The expected ACH is 0.2

You have no choice but to put in mvhr or dcv.

I can't see how you can put in a solid fuel range personally unless there are room sealed ones with dedicated air supplies.

BryanF

Ok well your look at 6inch holes in habitable room walls and extracts in wet rooms & kitchen. Seems a bit pointless imo
Start reading part L of the building regs

alemap83

Yea a solid fuel range that's needs an air supply is not suitable for a MVHR or DCV. Therefore we were just going to put in some wall air vents. Are there special wall vents that open based on humidity levels?

Yea I know it's a bit pointless doing the house airtight and then venting the walls but we can always change the range down the line and block up the vents.

sydthebeat

why a solid fuel range?

alemap83

My husband is insisting on one!! We both grow up with them in our houses and love the cosy affect of them.. He is a farmer and will be in and out of the house all day most days. He can keep it going. Also you once you pack it up they can last for hours lit whereas a stove would need to be lit again on return! Tried to talk him into a stove but couldn't. It's the only thing that he is demanding for the house. I can do what I want after that! That's why I gave in.. Plus I have to say I love them myself but for the sake of the airtightness and ventilation I was willing to give up on the idea.. Also we have lots of access to cheap fuel so from a heating perspective this was the cheapest option to us. We also couldn't find an airtight stove that could heat the house & provide hot water as good as the range.

I thought there were some new wall vents out there now that can be controlled better..

Calahonda52

alemap83 wrote: »

The expected ACH is 0.2

Why waste the time and effort and money on trying to get this when you are then going to punch all the Part L and F required holes through the fabric.

Have you done the math on a proper MVHR?

Lets do some math here:
[The following is based on some stuff I have read.
I think it is correct
but no representations or warranties attached]

Say 5 people at 30 cubic meters of free air per hour each, so 150 as the minimum air required

The max power consumption of any good quality rig is 0.45Wh per cubic meter.
so 67 watts is the power consumption
At 20 cent per kWh this makes c. euro 120 the annual running costs for 150

Now look at the heat recovery from it: if its 80% efficient
then the heat loss is 20%

so 150 by 20% is 30 cubic meters per hour (a)
The specific heat capacity of air is 0.33 Wh/(m cubed.degree Kelvin) (b)

The heating degree hours for Birr is 70k Kh/year (c)

Say heating by gas at euro 0.10 per kWh (d)

a by b by c by d gives you c euro 70 in heat loss from the MVHR
Which means you are recovering euro 280 which would otherwise be wasted.

So at an operational level you spend 120 pa to save 280 before cost of replacement filters so even if you spend the 160 on filters and maintenance
you have a vastly superior house from the point of view of airtightness, fresh air and constant comfort temperatures

BryanF

alemap83 wrote: »

My husband is insisting on one!! We both grow up with them in our houses and love the cosy affect of them.. He is a farmer and will be in and out of the house all day most days. He can keep it going. Also you once you pack it up they can last for hours lit whereas a stove would need to be lit again on return! Tried to talk him into a stove but couldn't. It's the only thing that he is demanding for the house. I can do what I want after that! That's why I gave in.. Plus I have to say I love them myself but for the sake of the airtightness and ventilation I was willing to give up on the idea.. Also we have lots of access to cheap fuel so from a heating perspective this was the cheapest option to us. We also couldn't find an airtight stove that could heat the house & provide hot water as good as the range.

I thought there were some new wall vents out there now that can be controlled better..

Take him to look at a log gasification boiler, load it in the garage, avoids fuel being brought daily through the house, more efficient, if house is built right and with large HW tank it might only be loaded/cleaned out once every two days. Then get an electric Stanley range for 'affect'

ht9zni1gs28crp

This is a whole different era and ball game of building!

The 'cosy' effect is memories of freezing houses and huddled around a stove...somewhat glossed over.

Go experience an airtight house in winter with MHRV and then tell me you 'want' a Stanley! Look up NZEB for more info...

sydthebeat

again its a case of people wanting what they know, rather than knowing what they want....

ht9zni1gs28crp

Its like asking the Ford dealer to remove Power steering and ABS from your 151 Focus because you have fond memories of your Mk2 Cortina and that was just grand without power steering or braking aids.

BryanF

ok lads, leave it there, we get the point, lets try to find ways of constructively helping the OP

ferryman35

I didn't stick to my guns and hold out for a range and it is the only thing I regret about our build. In fact if I knew then what I know now, it would have a few parts of the build much easier!

Anyway....

A range gives your house, and your kitchen a very good 'heart' (no pun intended!) I don't know if you noticed on a recent 'Room to Improve' the couple held out for their range cooker as a compromise and it worked out very well.

It can be done.....

You do need an external air supply - and depending on the model you choose maybe a substantial one- are you progressed too far to provide one? Up to 200mm sq which could probably be easier achieved by running 2x 100mm pipes and combining them near the range. Best practice is to run the pipes from one side of the house to the opposite to balance potential pressures from atmospheric conditions. (hard to get builders to do this)

These can be got with or without backboiler - personally, and especially since you are farming I think a boiler model would be a very good choice, because you may have a ready supply of wood?

These would be wood burning only... the pro's being that this will make a substantial contribution towards your renewable obligations, the con being that you need to have well seasoned wood - which usually means cut and stored for about 2 years (or kiln dried )

When combined with a solar thermal system, one can be used to compliment the other...i.e. when the solar contribution is at it weakest - you have the stove...and 'automatically' you probably wouldn't be lighting the stove during the mid summer months when the solar contribution is at its peak.

You can get a 'hot water cylinder' (thermal store) that will take a hot water feed from such a boiler and combine heat feeds from any other energy sources you may have such as solar / heatpump and a gas / oil boiler & immersion heater for backup. The stored energy in the cylinder is then supplied back to the heating system as required...whether conventional or underfloor. Your tap-hot-water is heated via a plate heat exchanger that is on the outside of the cylinder - what this means is that your 'consumable' hot water is heated on demand, and your hot water system operates at mains supply pressure - this makes balancing showers and kitchen taps much easier.

If you prefer pv solar you can use that energy to heat your water using the immersion heaters.


Then back to your original question......mhrv is now possible and I suspect very viable!

You would need to locate your kitchen extract point away from both your range and your 'normal' cooker, and put a good filter on that point. My own experience was that suppliers here didn't want to provide a filter at all.....not cool.

Anywhere you have a fuel burning appliance you do need a CO alarm for safety.

If you want specifics please let me know & I'll be happy to send you a pm.