Thinking of retrofitting HRV

peter2468

Hi guys

We've a 4 bed 1978 built bungalow which we've added new windows, cavity wall insulation and loft insulation too. We're now about to replumb, and seriously thinking about re-plastering, adding internal insulation and adding a HRV system.

My first query is: I wonder if it’s likely our current or future insulation levels (i.e. incl the dry lining) will be enough to mean the HRV will function well? Does dry lining on top of cavity wall insulation help a HRV system? Would it much better for the HRV performance/viability to add external insulation rather than adding the internal insulation?

Second query: Can HRV systems improve the air coming in (i.e. reduce pollutants from neighbours stoves etc)?

Any thoughts/advice much appreciated.

Plus any recommendations on HRV fitters appreciated via PM.

Thanks.

893bet

peter2468 wrote: »

Hi guys

We've a 4 bed 1978 built bungalow which we've added new windows, cavity wall insulation and loft insulation too. We're now about to replumb, and seriously thinking about re-plastering, adding internal insulation and adding a HRV system.

My first query is: I wonder if it’s likely our current or future insulation levels (i.e. incl the dry lining) will be enough to mean the HRV will function well? Does dry lining on top of cavity wall insulation help a HRV system? Would it much better for the HRV performance/viability to add external insulation rather than adding the internal insulation?

Second query: Can HRV systems improve the air coming in (i.e. reduce pollutants from neighbours stoves etc)?

Any thoughts/advice much appreciated.

Plus any recommendations on HRV fitters appreciated via PM.

Thanks.

Airtightness is more important than insulation level with regards HRV. How airtight is your house? Is it draughty etc. Chances are yes which needs to be addressed first.

peter2468

Thanks bet.

House was very draughty before the work we've done so far and we've certainly improve air tightness it a lot (new windows & front and back door. plus the cavity and loft insulation improves tightness too right?)

Not sure exactly how draughty it is now, so some kind of air tightness test probably the way to go?

Does drylining/internal-insulation itself typically improve air tightness at all?

BryanF

Insulation does not improve air-tightness

You need an air-tightness test carried out + fabric and energy assessment before considering Hrv

MicktheMan

peter2468 wrote: »

Hi guys

1.We've a 4 bed 1978 built bungalow which we've added new windows, cavity wall insulation and loft insulation too. We're now about to replumb, and seriously thinking about re-plastering, adding internal insulation and adding a HRV system.

2. I wonder if it’s likely our current or future insulation levels (i.e. incl the dry lining) will be enough to mean the HRV will function well?

3.Does dry lining on top of cavity wall insulation help a HRV system?

4.Would it much better for the HRV performance/viability to add external insulation rather than adding the internal insulation?

5.Can HRV systems improve the air coming in (i.e. reduce pollutants from neighbours stoves etc)?

6.Any thoughts/advice much appreciated.

1. Why do you feel a mvhr system is needed?
2. As others have said, the hr piece of the system depends on the air tightness of the structure amongst other things of which insulation isn't one.
3. see 2
4.External insulation (properly spec'ed) is far superior to internal insulation for a host of reasons but again nothing to do with mvhr
5.Imo, yes
6.I'm not sure where you got your information wrt mvhr and insulation levels but you are on the wrong track completely. Remember the main function of any ventilation system (incl mvhr) is to ventilate the space to the required level. The hr piece of mvhr is to recover most of the heat in the extracted air and transfer it to the incoming air. For this to work properly you need:

a. an airtight structure
b. an efficient ductwork design
c. ductwork to be within the thermal envelope of the structure

So some questions fro you to answer:

How air tight is my house?
Where will my ductwork run and how can I minimise the ductwork lengths?

Given the above there may be better ways for you to ventilate your house (google DCV - demand controlled ventilation, for example) or at least understand what you are trying to achieve before spending money on stuff you don't need / won't work (for example, by having the house tested/surveyed by an independent expert).

peter2468

> Why do you feel a mvhr system is needed?
The house is not ventilated at all at the moment (and the need to open windows has much increased since the work we have had done) so rather than installing wall vents etc some kind of smarter ventilation would be nice. MVHR, or DCV perhaps, sound like the best options if satisfactory air tightness can be achieved

I thought insulation and air tightness, while not exactly the same thing, went much more hand in hand than what you guys are suggesting. I thought external wall insulation would make the property much more airtight. Pumping a cavity where there are holes in the mortar must improve air tightness surely? But by what I think you are saying, air tightness and insulation are completely different things and share no common ground - though I do find it hard to believe (I have no construction experience and only a little knowledge though).

Thanks alot for replies and questions I need to answer / consider...