Integrating an MVHR to our build

[djcdan]

1 hour ago, Bitpipe said:

Fair enough but in your payback model factor in (if you have not already) that if you use in roof trays for PV you save the cost of covering that part with tile/slate.

Ideally, I'd just cover the garage roof, which is already preexisting so the roof is already there. If we were to cover the section of roof on the house, it would be a £200 saving.

 

1 hour ago, Bitpipe said:

Also VAT free if you do it now vs later.

Yes, can see the benefit of that.

 

56 minutes ago, SteamyTea said:

PV now costs less than single glazed windows and frames.  There has to be a point where it cannot get any cheaper as the materials will not get any cheaper.

I don't dispute the price decline, just the technology and the efficiency of that technology. If it takes 10 years to pay back, I can 100% guarantee that the tech will significantly mature well within that period to the point where the current models are relics. It feels like purchasing a PC circa year 2005 and then having to use that PC until at least 2015 to get your moneys worth. In that 10 year span, tech had moved on so far that the units purchased in 2005 where obsolete. The tech still doesn't do what we all want it to do - become self-sufficient (unless you throw £££ at it - but that will come. I would rather pay £10k for a system in 5 years and gain an £8k grant from the government (which will be offered at some stage as they chase their green targets), so a net cost of £2k, to get a system that does what is needed - generate enough electricity to be self-sufficient, rather than be stuck with a system installed now that partially does the job and spend more money to do so since there is no grant or FiT (or similar).

 

33 minutes ago, Bitpipe said:

To be pedantic you need 7600mm2 so 10mm for standard width door but obv less if your door is wider

 

Good to know that. Cheers. The store cupboard door is a skinny one - 686mm. Which would there make it a 11mm gap.

[SteamyTea]

4 minutes ago, djcdan said:

just the technology and the efficiency of that technology

There are fundamental limits to the technology (~37% for silicon), and in real terms, we are not far off them.  HIT is at around 25% and has been for about a decade.

Inverters peak at about 95%, so not a lot not be gained there.

 

I once had a conversation with a lady that had a small wind turbine, a 1 kW one.  She was asking me what sort of washing machine to get as she was off grid.

She never did understand that it would not do her washing, even 'when it was very windy'.

 

 

[Rich123]

Hi haven’t followed all the threads but I will offer a little advice.

1. install the MVHR on. Solid wall , if not use isolating mounts to ensure that there is no vibration.

2. install flexible ducts on the final connections.

3. consider using attenuators in the duct work,

On the external connections And Between rooms .

4. Use pre insulated ductwork 

5 . Make sure there is no requirement for fire control, normally on the means of escape you would need to install fire stops. Worth checking. 
make sure inlet and outlets are 3 mtr apart if possible.

6  Use an approved contractor for installation 

7.  Use bends with splitters in , these are much lower resistance than standard.

Re calculations , I didn’t see the whole house air change rate which boost needs to meet .

Keeping the velocity low will improve the noise levels also as this will reduce the pressure loss of the system.

 

Re heating , I would heat every room , no discussion. Especially if you ever want to sell the house.

NHBC set standards for design and I would ensure that these are met in every room.

 

 

Rich

 

Edited January 6, 2021 by Rich123
Added note

[djcdan]

4 minutes ago, SteamyTea said:

There are fundamental limits to the technology (~37% for silicon), and in real terms, we are not far off them.  HIT is at around 25% and has been for about a decade.

Inverters peak at about 95%, so not a lot not be gained there

Going back to the PC analogy, I am not comparing a PC running XP (2005) to a PC running Windows 10 (2015). I am comparing the movement of the general technological shift from PC to smartphones/tablets/ultrabooks. With the amount of focus on green energy, new technology will enter the space to meet the demand of this growing sector. There has never been an industry, product or sector that has completely plateued technologically speaking, especially one that still seems relatively young in the growth cycle of that market.

[Rich123]

Re ASHP, if your using an ASHP underfloor heating is the best solution.

Hot water would be generated by a cylinder with an electrical boost , Daiken do a system for both that integrates well.

 

[SteamyTea]

17 minutes ago, djcdan said:

There has never been an industry, product or sector that has completely plateued technologically speaking, especially one that still seems relatively young in the growth cycle of that market.

The industry is pretty mature really.  Just not been in the public's consciousness until recently.

It is a bit like planting a tree, the best time was 20 years ago, the second best time is today.

[djcdan]

1 minute ago, SteamyTea said:

The industry is pretty mature really.  Just not been in the public's consciousness until recently.

It is a bit like planting a tree, the best time was 20 years ago, the second best time is today.

Perhaps. It just feels like covering a roof to generate 30p per sunny hour doesn't offer the mature solution that the world currently requires. If a product was launched with x5-10 efficiency at a strong price point, it would revolutionise the industry over night. If there is money to be made, you can be sure someone is working on development.

 

Nethertheless, even if the tech remains the same, the government will eventually need to support installations, which they currently don't do. In Scotland, an ASHP that would have cost me £10k in 2020 will cost me £2.5k in 2021 as a result of grants. Support for PV will come. Eventually... And plus, I need to wait for smart meter support in our area anyway. ?

 

[SteamyTea]

25 minutes ago, djcdan said:

If a product was launched with x5-10 efficiency at a strong price point,

Ain't going to happen, that would be more energy coming out than goes in.

The price point is an interesting one.  We are now about about £500/kW installed, or about £100/m².

That is about £50/m² cheaper than a Wickes PVC window.

[DavidO]

2 hours ago, Rich123 said:

NHBC set standards for design and I would ensure that these are met in every room.

 

 

NHBC are a joke....!!!

[Bitpipe]

19 hours ago, Rich123 said:

Re heating , I would heat every room , no discussion. Especially if you ever want to sell the house.

NHBC set standards for design and I would ensure that these are met in every room.

 

I would respectfully disagree on that last point.

 

In a near passive house (and I have lived in mine coming up on 5 years) it is really not needed.

 

We have a 110m2 passive basement, no heating whatsoever and is always 22^oC. Ground floor (same foot print) has low temp wet UFH which is active year round and set to 22^oC but only comes on Nov-Feb and even then only on the really cold days. First floor bedrooms have no heating and are always comfortable (21 usually) due to solar gain, convected heat from the rest of the house and occupancy.

 

Bathrooms have electric UFH as tiles will feel cold even at an acceptable room temp and wet ufh towel rails. Rooms in roof have no heating but always warm due to solar gain (roof-lights) and convection.

 

If there was heating installed where it is not, it would never be on so the invested cost would be wasted until such times as the house needed sold (which is no time soon). 

 

If I really wanted heat in bedrooms, I'd just plug panel heaters into the wall.

 

I don;t have much time for NHBC to be honest, especially looking at the appalling design and quality of the builders boxes churned out annually that all meet NHBC standards.

[DavidO]

10 minutes ago, Bitpipe said:

 

I would respectfully disagree on that last point.

 

In a near passive house (and I have lived in mine coming up on 5 years) it is really not needed.

 

We have a 110m2 passive basement, no heating whatsoever and is always 22^oC. Ground floor (same foot print) has low temp wet UFH which is active year round and set to 22^oC but only comes on Nov-Feb and even then only on the really cold days. First floor bedrooms have no heating and are always comfortable (21 usually) due to solar gain, convected heat from the rest of the house and occupancy.

 

Bathrooms have electric UFH as tiles will feel cold even at an acceptable room temp and wet ufh towel rails. Rooms in roof have no heating but always warm due to solar gain (roof-lights) and convection.

 

If there was heating installed where it is not, it would never be on so the invested cost would be wasted until such times as the house needed sold (which is no time soon). 

 

If I really wanted heat in bedrooms, I'd just plug panel heaters into the wall.

 

I don;t have much time for NHBC to be honest, especially looking at the appalling design and quality of the builders boxes churned out annually that all meet NHBC standards.

Agree 100%......Our build/size/heating configuration is very similar to bitpipe’s and (7years in) our bedrooms are consistently comfortable with no installed heating.

[ProDave]

Another one here with no heating upstairs apart from the bathroom and en-suite.

 

In the middle of a cold spell in the Highlands, -8 last night, -9 the night before, barely been above 0 even in the day for nearly 2 weeks now.  Downstairs 21 degrees, upstairs 18.7 degrees.

[Bitpipe]

22 hours ago, djcdan said:

Going back to the PC analogy, I am not comparing a PC running XP (2005) to a PC running Windows 10 (2015). I am comparing the movement of the general technological shift from PC to smartphones/tablets/ultrabooks. With the amount of focus on green energy, new technology will enter the space to meet the demand of this growing sector. There has never been an industry, product or sector that has completely plateued technologically speaking, especially one that still seems relatively young in the growth cycle of that market.

 

Moore's law (where the number of transistors on a given area doubled every 12-24 months) drove much of the innovation and upgrade cycle of computing and into that I'd lump desktop machines,  mobile devices, wearables etc.  However after 50 years that itself has now more or less plateaued.

 

 

22 hours ago, djcdan said:

Perhaps. It just feels like covering a roof to generate 30p per sunny hour doesn't offer the mature solution that the world currently requires. If a product was launched with x5-10 efficiency at a strong price point, it would revolutionise the industry over night. If there is money to be made, you can be sure someone is working on development.

 

Nethertheless, even if the tech remains the same, the government will eventually need to support installations, which they currently don't do. In Scotland, an ASHP that would have cost me £10k in 2020 will cost me £2.5k in 2021 as a result of grants. Support for PV will come. Eventually... And plus, I need to wait for smart meter support in our area anyway. ?

 

 

Is a smart meter now a pre-requisite for a private PV system?

 

The govt, through the energy providers, had already subsidised PV through the FIT, but that seemed to artificially keep prices high, especially installation which had to be MCS approved.

 

Once that went, prices dropped so you're now paying £4k for a system that would have set you back maybe twice as much five years ago. Admittedly the payback is still longer but you still get appreciable generation year round and if you adjust your consumption to match (time appliances to run in daytime) it will all add up. Using PV in summer to drive cooling appliances, such as a split aircon or ASHP cooling your slab makes perfect sense.

 

The problem is still storage (which is essentially battery technology) which is evolving very slowly and still mega expensive. 

 

We have a PV diverter to the hot tank which cost a few hundred and has easily paid for itself, probably more than once already. 

[Rich123]

5 hours ago, Bitpipe said:

 

I would respectfully disagree on that last point.

 

In a near passive house (and I have lived in mine coming up on 5 years) it is really not needed.

 

We have a 110m2 passive basement, no heating whatsoever and is always 22^oC. Ground floor (same foot print) has low temp wet UFH which is active year round and set to 22^oC but only comes on Nov-Feb and even then only on the really cold days. First floor bedrooms have no heating and are always comfortable (21 usually) due to solar gain, convected heat from the rest of the house and occupancy.

 

Bathrooms have electric UFH as tiles will feel cold even at an acceptable room temp and wet ufh towel rails. Rooms in roof have no heating but always warm due to solar gain (roof-lights) and convection.

 

If there was heating installed where it is not, it would never be on so the invested cost would be wasted until such times as the house needed sold (which is no time soon). 

 

If I really wanted heat in bedrooms, I'd just plug panel heaters into the wall.

 

I don;t have much time for NHBC to be honest, especially looking at the appalling design and quality of the builders boxes churned out annually that all meet NHBC standards.

Hi yes I understand the argument , and passive house is designed to require minimal heating. I am not a passive house designer but the standard for this is very high, not only U values but zero cold bridges , building orientation etc.

This is a fabric first approach and I’d agree that under these circumstances then you should be fine. However as a designer I would want to ensure that any design is 100% suitable for use . People use houses in different ways and from what I gather from this thread there has been no detailed thermal analysis to support what the system will achieve. If I was buying a house with no heating in the bedrooms , I would want to have supporting evidence that this is an engineered solution and not a guess.

[djcdan]

2 hours ago, Bitpipe said:

Moore's law (where the number of transistors on a given area doubled every 12-24 months) drove much of the innovation and upgrade cycle of computing and into that I'd lump desktop machines,  mobile devices, wearables etc.  However after 50 years that itself has now more or less plateaued.

Yes, certainly does. For the time being, I see hardware advances slowing whilst advances in communications and technology such as blockchain advancing everyday use of tech.

 

2 hours ago, Bitpipe said:

Is a smart meter now a pre-requisite for a private PV system?

 

I read somewhere on BH it was needed to sell electricity back to the grid....

 

2 hours ago, Bitpipe said:

The problem is still storage (which is essentially battery technology) which is evolving very slowly and still mega expensive. 

 

Yes. Would be good not having a massive bank of batteries in the corner. As we don't have gas available where we are, I'm keen to have battery storage on site so that in the event of a power cut, we can still heat the house (no wood burning stove). The longest power outage (according to neighbours as it predates us living here) is just under 2 weeks. 2 weeks during winter - it'll bound to be during winter - with no heating and particularly hot water could be an experience!

[Rich123]

23 hours ago, DavidO said:

 

NHBC are a joke....!!!

I am talking about thermal design . There are a number of standards , but NHBC or CIBSE are the 2 industry recognised standards.

I would  agree that maybe some of this is out dated. But if there is an issue then at least it’s a recognised standard.

Having investigated a number of issues with homes the first thing I would do was ask for the specified standard and the calculations.

 

[ProDave]

1 minute ago, Rich123 said:

I am talking about thermal design . There are a number of standards , but NHBC or CIBSE are the 2 industry recognised standards.

I would  agree that maybe some of this is out dated. But if there is an issue then at least it’s a recognised standard.

Having investigated a number of issues with homes the first thing I would do was ask for the specified standard and the calculations.

 

I think the big issue is air tightness.  You can say what you want in a specification, but if the person doing the work does not take care or does not understand what or why he is doing it, the results can be poor.  At least now a new build is supposed to have an air test done, so you should get a real figure of how well it has been done.

 

It is very easy to fit the required amount of insulation in such a poor way that it is ineffective, I have seen it plenty of times, but there is no easy way to measure how well it has actually been done.

[Rich123]

18 minutes ago, ProDave said:

I think the big issue is air tightness.  You can say what you want in a specification, but if the person doing the work does not take care or does not understand what or why he is doing it, the results can be poor.  At least now a new build is supposed to have an air test done, so you should get a real figure of how well it has been done.

 

It is very easy to fit the required amount of insulation in such a poor way that it is ineffective, I have seen it plenty of times, but there is no easy way to measure how well it has actually been done.

Yes air tightness is the issue , and with testing that’s a huge improvement over the past few years.

Also Insulation , but also cold bridging which is important ( also a requirement of SAP).

And I accept that there are issues with specifications of heating and real life values . Also there is a requirement for intermittent operation and that is also a big issue. I had an issue with some holiday homes and ASHP , they took forever to heat up , and I had advised a remote system to allow systems to be turned on in advance but it was removed to save money. Hence I’m a little safe when it comes to design.

[NSS]

On 16/12/2020 at 16:21, djcdan said:

 

We've currently speced Rationel double glazing units for the windows, which have a rating of 1.2. The velux's in the bedrooms (it's a 1.5 storey) have a rating of 1.3 and there are two in each room.

 

I've not had PHPP modelling. Is this something that could be calculated myself, or best left with the architect?

 

Late to this thread so apologies if what I'm about to add has already been covered. We have a 1.5 storey (chalet bungalow) of total 165m2 of which is split circa 75% ground floor to 25% first floor. We have wall and roof circa 1.4, Windows 0.7, airtightness of 1.6, Panasonic 9Kw ashp, Paul Novus 300 mvhr and an EPC score of 96. Not the best on here but not bad, but we still find during really cold spells (we're on the south coast so we're not talking Scottish Highlands cold) that we appreciate the Panasonic air rad in our bedroom. As already said, mvhr won't spread the heat and even in a well insulated house we find very little heat finds it's way upstairs (though that may in part be due to our design which has the staircase in a floor to vaulted roof space that has outside walls to three sides).

 

I suspect someone somewhere later in the thread will have suggested at least making provision for some heating upstairs, but if not then I'd strongly recommend it. Easier not to use it than find you need it when it's too late to add.

[Iceverge]

1 hour ago, Rich123 said:

Hi yes I understand the argument , and passive house is designed to require minimal heating. I am not a passive house designer but the standard for this is very high, not only U values but zero cold bridges , building orientation etc.

This is a fabric first approach and I’d agree that under these circumstances then you should be fine. However as a designer I would want to ensure that any design is 100% suitable for use . People use houses in different ways and from what I gather from this thread there has been no detailed thermal analysis to support what the system will achieve. If I was buying a house with no heating in the bedrooms , I would want to have supporting evidence that this is an engineered solution and not a guess.

 

There is a sheet in PHPP advising if additional heating is needed in specific rooms. A certified passivhaus (a controlled standard)  should perform as per PHPP. 

 

On the other hand "passive house" as an uncontrolled term and offers no guarantees unless you ensure adequate oversight yourself. 

[ProDave]

1 hour ago, NSS said:

I suspect someone somewhere later in the thread will have suggested at least making provision for some heating upstairs, but if not then I'd strongly recommend it. Easier not to use it than find you need it when it's too late to add.

I provisioned for a dedicated electric point in each bedroom for a small panel heater.

 

They have not been needed and not installed and those points remain unused.  But I am still glad I put them in.

[joe90]

2 hours ago, NSS said:

I suspect someone somewhere later in the thread will have suggested at least making provision for some heating upstairs, but if not then I'd strongly recommend it. Easier not to use it than find you need it when it's too late to add.

I did not think special provision fir dedicated points were necessary as each room has plenty of 13amp sockets and all panel heaters etc come with a 3 pin plug (and timer and thermostat if required).

[NSS]

6 minutes ago, joe90 said:

I did not think special provision fir dedicated points were necessary as each room has plenty of 13amp sockets and all panel heaters etc come with a 3 pin plug (and timer and thermostat if required).

 

Depends on what sort of provision you're making I guess, Joe. In our case, the addition of the Panasonic Air Rad required both a dedicated fused spur and the supply/return loop for heated (or cooled) water from the ASHP. As you know, the provision of cooling capacity was as important for us as heating capacity due to our requirement to keep a sealed environment for air quality.

[Rich123]

On 05/01/2021 at 17:02, DavidO said:

Dont get too hung up on the calculations. Remember that, at your stage of the process, they include some important assumptions rather than realities, which, in effect, means they are (hopefully intelligent) guesswork. The prime example in our case, which was where the architects energy consultant slipped up, was airtightness. Her calculations were based on 3 (cu.m/hr/m.sq @ 50Pa) which,  as first time self-builders, was the very best she was prepared to believe we could achieve, whereas the actual result was 0.296. Fortunately we had stuck to our guns as regards omitting the bedroom heating (significant cost saving + Yorkshire genetics) but still ended up over speccing the boiler and including a wood burning stove which we have lit less than a dozen times in 7 years.

 

I it won’t effect the SAP as it’s based on the system not individual room heating .

Most SAP assessors won’t be designers. 
 If you add electric heating points then that will effect the SAP so if you are going to I’d keep that quiet.

[ADLIan]

SAP always includes a heating system,  if none specified then default is electric so no need to hide any dedicated outlets.