Benefit Measurement?

[JamesJJJ]

In relation to my other thread which is uncovering a multitude of issues with the mvhr installed in my house I keep coming back to the same point.

 

In my case I think the mvhr was installed as a luxury item to help sell the house; nowhere near enough care was taken in its implementation and commissioning for it ever to deliver it's real potential.

 

This leads me onto a question, how would you go about measuring the benefit of such a system?

 

From what I have learned the benefits of an mvhr are:

1. Cleaner, fresher air.

2. Elimination of damp/condensation problems in wet areas.

3. Reduction in heat requirement as a consequence of reclaiming heat that would be lost to the outside. 

 

1 can be measured with an air quality meter so this is fairly easy? Less dust, fewer chemicals,  lower co2?

2 can also be measured with an air quality meter and subjectively the presence/absence of condensation/mould can be seen?

3 is the one I am unsure on. I think this will be massively impacted by ambient weather and building use? As a result I think measuring this cost/benefit ratio would be very difficult?

 

In my case I am trying to work out if the cost of running/maintaining such a system provides benefits which justify this effort/expense vs opening windows and paying more for heating/ventilation. I would think this analysis/calculation applies to anybody considering such a system?

 

Thanks,

 

 

 

Edited August 16, 2019 by JamesJJJ

[PeterW]

3 minutes ago, JamesJJJ said:

In my case I think the mvhr was installed as a luxury item to help sell the house; nowhere near enough care was taken in its implementation and commissioning for it ever to deliver it's real potential.

 

It may actually be a building regs requirement. If you don’t have external vented fans for bathrooms, and if windows don’t have trickle vents fitted,  then it has to have MVHR. 

 

That would be my starting point. 

[JamesJJJ]

Yes, so this is more focussed on points 1&2 rather than minimising environmental impact under point 3? 

 

 

 

[PeterW]

If you don’t have trickle vents then it’s purely about item 2, with item 1 as an added benefit

[Gone West]

7 hours ago, JamesJJJ said:

In my case I think the mvhr was installed as a luxury item to help sell the house; nowhere near enough care was taken in its implementation and commissioning for it ever to deliver it's real potential.

What is your airtightness value? If it was installed as a luxury item, is it needed?

[ProDave]

The purpose of mvhr is to ventilate the house just enough to give fresh air, while trying to recover as much of the otherwise lost heat as possible.

 

Any other system, e.g trickle vents, gives very variable ventilation rates without any heat recovery so all the air that leaves, leaves warm, with all that wasted heat.  In still weather it may not ventilate enough.

 

You have to have an air tightnes test now and if it is better than a certain figure, you must fit it.  I remember a new build that was not planning it a couple of years ago being forced to fit it once the air tight test was done.

 

Condensation is a separate issue. With good insulation that should never happen.  Ventilation is often quoted as the "solution" to condensation but it is not really, it is just removing the moisture so there is nothing to condense on the still cold surfaces.

[Temp]

To calculate the power being recovered by the mvhr you need to know the flow rate, external air temp, and the temperature of the air delivered to rooms by the mhrv. All of which can be measured.

 

Edited August 17, 2019 by Temp

[mvincentd]

I guess all units differ but maybe dig around in the menu....mine has status-energy-power consumption-avoided heating/avoided cooling-total savings.

[JamesJJJ]

On 17/08/2019 at 01:21, Temp said:

To calculate the power being recovered by the mvhr you need to know the flow rate, external air temp, and the temperature of the air delivered to rooms by the mhrv. All of which can be measured.

 

I was going to do that at some point but I am more interested in working out the cost (in CO2 and £) of using the unit + less heating vs leaving the windows on vent and running the heating more.

[JamesJJJ]

On 17/08/2019 at 09:45, mvincentd said:

I guess all units differ but maybe dig around in the menu....mine has status-energy-power consumption-avoided heating/avoided cooling-total savings.

That is a nifty feature. The control panel of our Villavent is not as sophisticated:

 

[Mr Punter]

3 minutes ago, JamesJJJ said:

I was going to do that at some point but I am more interested in working out the cost (in CO2 and £) of using the unit + less heating vs leaving the windows on vent and running the heating more.

 

The main areas that need extract ventilation are kitchens, bathrooms and utilities. Although leaving a window open slightly is better than nothing, mechanical extract is far more effective at removing the moist air.

 

The heat recovery bit is a nice-to-have but not essential IMO.