Heat Recovery System Information

Lemlin

Hi folks,

Just wondering if someone could give me some quick information on heat recovery systems. I know there's plenty of information available but I'm keen to cut through all the BS and get to the truth. I'd also like to get people's opinions on them. I'm at sub floor level on my project and just got the pipes fitted for the central vacuum system. However, the agent from there mentioned a heat recovery system and said that they could do one for 7k. I've had a quick look and there seems to be plenty of information about them but I'm wondering if someone could explain in layman's terms what they do?
Bearing in mind that I am going with a geothermal underfloor heating system. Not sure if that effects it or not.

The agent said a heat recovery system would negate the need for vents in my house when built and would result in 80% of heat being kept. The price though is 7k which sounds steep.

From people's experiences and knowledge, are they worth it and what way do they work?

JuniorB

Numerous threads on it here. Do a quick search ..
In a nut shell...the more air tight your house, the better it will work.
7k seems very steep. How big is your house? Around the 5k mark is what most quoted me - we've a 3100sq ft house that needs 2 HRV units due to layout.

If you decide to go with it here's a list of Q's for potential suppliers that I compiled from the various threads ...

General:
1. Can you show the calculation of how you sized the units suitability for our house?
2. I assume there is a boost function for showers, kitchen etc. How does this operate? Is it on a sensor or switch, can the time it runs be adjusted etc
3. Should we put an extract in our utility room so we can dry clothes etc?
4. Can the control unit display inlet and distribution air temp?
5. Is the system sound proofed, what is the operating sound level?
6. How often should the filters have to be replaced?
7. How much are filters, where can I get them from?
8. How often is servicing required?
9. We are thinking of getting a cooker hood with graphite/charcoal filters running in recirculation mode to deal with grease & cooking smells and let the HRV deal with the steam. What are your opinions/preferences with this?
10. Have you made any provision for a fire out break in our house? Fire rated valves, electrical cut out etc.
Ducting:
1. Are we using rigid ducting in general?
2. Where are we using flexible ducting?
3. Is the ducting insulated and with what?
4. What way is the air delivered? Is it a single pipe that progressively gets smaller to vary the pressure or do all the pipes lead to/from a manifold?

Siting of the Unit(s):
1. I’ve been advised to create a 150mm plinth for your unit to sit on - from rigid insulation (supposedly this dampens vibrations) … what are you opinions on this?
2. Is our attic hatch large enough to get the unit in through?
3. We should try and keep the unit near our attic hatch, so regular maintenance is easier - not disturbing other insulation etc. …and have a light near by!
4. Could we place the main units over a hallway/ bathroom in our attic space, to minimize sound transfer to bedrooms etc ?

Inlets:
1. Should we position the inlet and outlet pipes on opposite sides of the building? Is there any advantage with this?
2. I assume we should keep the inlet pipe away from chimneys – should it be northern facing (bringing in colder air) or southern facing or does it matter really?

Best of luck with the rest of your build.

gman2k

Lemlin wrote: »

Hi folks,
I'm keen to cut through all the BS and get to the truth.

If you are building a new house and you meet the required airtightness standard (which you have to by law) then it's more or less a given that MHRV is the only way to go. (unless you want to double the size of the air vent 'holes in your walls)

After that, it's a question of which supplier.
Have a read of different literature from suppliers - you should be able to see through the sales pitch yourself and see the benefits.

Lemlin

Just a couple of questions -

1. When does the Heat recovery system have to be fitted? For example, at what stage would I need to get the supplier in?
2. We plan to have an open fire in the sitting room. I have been told that its impossible to have a heat recovery system with an open fire. However, one builder told me that an item can be put in the chimney and it is possible then to have a heat recovery system. Is that true?
3. Some people speak of heat recovery and then of MHRV? I presume they are both the same system?

The house size is 3151 square foot.

sunnysoutheast

Just a couple of questions -

1. When does the Heat recovery system have to be fitted? For example, at what stage would I need to get the supplier in?
>> Ducting installed at first fix electrics/plumbing stage. Commissioning and balancing after air tightness testing.
2. We plan to have an open fire in the sitting room. I have been told that its impossible to have a heat recovery system with an open fire. However, one builder told me that an item can be put in the chimney and it is possible then to have a heat recovery system. Is that true?
>> You need a room-sealed stove with an external air supply.
3. Some people speak of heat recovery and then of MHRV? I presume they are both the same system?
>> MHRV stands for Mechanical Heat Recovery Ventilation, so yep!


We have HRV. Along with CAT5e cable everywhere it's the best thing we put in!

SSE

Lemlin

I have been advised by a supplier - "If your intention is to only light the fire occasionally, then there is a
baloon available to close the chimeny."

Lightning McQue

Sunnysoutheast

What size is your house and what unit did you install?

Did u triple glaze the windows and put in geo-thermal?

Where are you based?

Lightning

sunnysoutheast

Lemlin wrote: »

I have been advised by a supplier - "If your intention is to only light the fire occasionally, then there is a
baloon available to close the chimeny."

Might be worth searching/asking for experiences of these. Not sure how the draw on the open chimney when lit would interact with the HRV extracts, for example whether smoke would be drawn out into the room. With the room sealed stoves with external air supply this is negated (except when loading) - trouble is there's not too many of those around and those that there are can be pricey.

SSE

Lightning McQue

sunnysoutheast

Where did you get your stove?


Lightning

sunnysoutheast

Lightning McQue wrote: »

sunnysoutheast

Where did you get your stove?


Lightning

As per the rules I've just sent you a PM with the suppliers in it!

No geothermal. We're not airtight as such, but did upgrade insulation and windows over the regs. in force when we designed in 2005 and seal round opes etc. I recognise that this will make HRV less efficient but the main driver for us was internal air quality and lack of flies etc., we live in a rural area. We put in two separate units as we built a (stupidly big) 4500sq.ft.!

SSE

imitation

A good first port of call is the SAP Appendix Q, its the english energy ratings body, they have a good section on MHRV, and any unit worth there salt should be listed on this. They also have a very helpful installation list, http://www.sap-appendixq.org.uk/documents/MVHR_Installation_Guide_Final.pdf

The open fireplace is a no go in my books, you may be able to seal it with some sort of balloon device, but think of the practicalities of it, how airtight can it be ? What if somebody forgets its there and lights the fire ? Where will you put this soot covered thing when you do want go to light your fire ? The only way to go in my opinon is an airtight stove. You can do very nice fireplaces with inset or free standing stoves.

For the kitchen extract, you can get a special valve from some manufacturers than will block off the external extract pipe when its not in use. I think this is preferable to a charcoal filter, which has to be replaced periodically, and may not block 100% of odours. You should also watch out for the warrenty on your extract unit itself, it specifies the spec pipe for extraction etc, so its possible to invalidate it.

Lemlin

I've been quoted 6k from a supplier who I've heard good things about in Galway. Going to think about it for a few weeks.
The open fire is non negotiable so we have to go with it.

sunnysoutheast

Lemlin wrote: »

I've been quoted 6k from a supplier who I've heard good things about in Galway. Going to think about it for a few weeks.
The open fire is non negotiable so we have to go with it.

I think you might be looking at the same supplier we used.

I'd honestly think about the open fire, all the work you'll put in and pay for to get airtightness could be compromised.

SSE

Lemlin

sunnysoutheast wrote: »

I think you might be looking at the same supplier we used.

I'd honestly think about the open fire, all the work you'll put in and pay for to get airtightness could be compromised.

SSE

Should we also be going with triple glazed windows? The company we are going to, large South based company in a certain province(!), have triple glazed windows that have a U value of .7 and also premium triple glazed with a U value of .5. Will they be very expensive though?

sas

Lemlin wrote: »

Should we also be going with triple glazed windows? The company we are going to, large South based company in a certain province(!), have triple glazed windows that have a U value of .7 and also premium triple glazed with a U value of .5. Will they be very expensive though?

They have triple glazing with a u-value of 0.7.

The u-value of the window is around 1.2 as I understand it.

The frame typically is a considerably worse insulator than the glazing and hence makes the overall u-value worse.

Whether you need triple glazing or not is difficult to answer. In terms of bang for buck, aiming for a high level of airtightness would likely contribute more to comfort and lower bills than opting for triple glazing over double in a house with a poor level of airtightness.

In a nutshell, you can have the best windows in the world but if you leave the front door open they won't get the chance to provide a benefit.

Lemlin

sas wrote: »

They have triple glazing with a u-value of 0.7.

The u-value of the window is around 1.2 as I understand it.

The frame typically is a considerably worse insulator than the glazing and hence makes the overall u-value worse.

Whether you need triple glazing or not is difficult to answer. In terms of bang for buck, aiming for a high level of airtightness would likely contribute more to comfort and lower bills than opting for triple glazing over double in a house with a poor level of airtightness.

In a nutshell, you can have the best windows in the world but if you leave the front door open they won't get the chance to provide a benefit.

Would there be a big difference between the price of triple and double glazing?
Our plan is to get Homebond to do an air tightness test and tape up any ducts etc. that need taping.

sas

Lemlin wrote: »

Would there be a big difference between the price of triple and double glazing?
Our plan is to get Homebond to do an air tightness test and tape up any ducts etc. that need taping.

It depends on the windows the glazing is going into.

For example, I've had quotes of 45k for passive house grade triple glazed windows. If I dropped the glazing to double it fell to 42k i.e approx 7% more for triple glazing.

If however your budget is for standard pvc windows, the price for the upgrade to triple glazing could be a considerable percentage and the decision will come down to how price sensitive you are.

You're going to have to ask the supplier basically.

Lemlin

sas wrote: »

It depends on the windows the glazing is going into.

For example, I've had quotes of 45k for passive house grade triple glazed windows. If I dropped the glazing to double it fell to 42k i.e approx 7% more for triple glazing.

If however your budget is for standard pvc windows, the price for the upgrade to triple glazing could be a considerable percentage and the decision will come down to how price sensitive you are.

You're going to have to ask the supplier basically.

Its PVC windows we will be fitting. The house is 3151 square foot and has 29 windows in total so the windows could be expernsive. Most windows range from 900 to 1200.

soldsold

The supplier you are referring to has 1.2 u-value triple glazing in Aluclad timber, I believe their PVC double glazing should be around a similar value, I would be surprised if the PVC double glazing u-value was outside the range of 1.1 to 1.4, as SAS says the best bet is to give them a call and make sure they quote the whole window value not just the glass.

daveoc16

JuniorB wrote: »

Numerous threads on it here. Do a quick search ..
In a nut shell...the more air tight your house, the better it will work.
7k seems very steep. How big is your house? Around the 5k mark is what most quoted me - we've a 3100sq ft house that needs 2 HRV units due to layout.

If you decide to go with it here's a list of Q's for potential suppliers that I compiled from the various threads ...

General:
1. Can you show the calculation of how you sized the units suitability for our house?
2. I assume there is a boost function for showers, kitchen etc. How does this operate? Is it on a sensor or switch, can the time it runs be adjusted etc
3. Should we put an extract in our utility room so we can dry clothes etc?
4. Can the control unit display inlet and distribution air temp?
5. Is the system sound proofed, what is the operating sound level?
6. How often should the filters have to be replaced?
7. How much are filters, where can I get them from?
8. How often is servicing required?
9. We are thinking of getting a cooker hood with graphite/charcoal filters running in recirculation mode to deal with grease & cooking smells and let the HRV deal with the steam. What are your opinions/preferences with this?
10. Have you made any provision for a fire out break in our house? Fire rated valves, electrical cut out etc.
Ducting:
1. Are we using rigid ducting in general?
2. Where are we using flexible ducting?
3. Is the ducting insulated and with what?
4. What way is the air delivered? Is it a single pipe that progressively gets smaller to vary the pressure or do all the pipes lead to/from a manifold?

Siting of the Unit(s):
1. I’ve been advised to create a 150mm plinth for your unit to sit on - from rigid insulation (supposedly this dampens vibrations) … what are you opinions on this?
2. Is our attic hatch large enough to get the unit in through?
3. We should try and keep the unit near our attic hatch, so regular maintenance is easier - not disturbing other insulation etc. …and have a light near by!
4. Could we place the main units over a hallway/ bathroom in our attic space, to minimize sound transfer to bedrooms etc ?

Inlets:
1. Should we position the inlet and outlet pipes on opposite sides of the building? Is there any advantage with this?
2. I assume we should keep the inlet pipe away from chimneys – should it be northern facing (bringing in colder air) or southern facing or does it matter really?

Best of luck with the rest of your build.

Just a quick question: Instead of a MHRV unit, would vented windows do the trick? At least these can be opened/closed as desired, and you don't need a hole in the wall for ventilation then.
I'm putting in an open fire in one room and a stove in another. It's a new build and very well insulated. Seems like a lot of trouble to start installing seperate vents for fireplaces/stoves.Especially as it seems to be yet untested on a meaningful scale. Maybe I'm missing something...??

gman2k

daveoc16 wrote: »

Just a quick question: Instead of a MHRV unit, would vented windows do the trick? At least these can be opened/closed as desired, and you don't need a hole in the wall for ventilation then.
I'm putting in an open fire in one room and a stove in another. It's a new build and very well insulated. Seems like a lot of trouble to start installing seperate vents for fireplaces/stoves.Especially as it seems to be yet untested on a meaningful scale. Maybe I'm missing something...??

A hole in a window frame letting in cold outside air is the same as a hole in a wall letting in cold outside air. Vented windows will provide ventilation alright, but there is no heat recovery from this form of ventilation.
What is your airtightness strategy?