Hi to all

[Simon R]

Hi and thank you to all forum members for creating a very useful resource.
Having managed to get planning permission my wife and I are about to start on our first self build. We intend to do as much work on the project as we can, we done several projects in the past but nothing on this scale
After a lot of looking at various build systems we have opted to use the JUB ICF sytem. Our intent is to get as low energy build as we can with our budget.
A little bit about the project: The house is in the region of 200M2 over two floors. The MVHR we are looking at the Genvex 185 unit which also gives us an integrated air source heat pump. We have not made a decision on windows yet but have Velfac on the short list.

[Ian D]

 Just seen shocking reviews on velfac , we unsure about windows too

 

[Alexphd1]

Hi and welcome.

The jub package looks very interesting, are you using the whole package (insulated raft, icf walls and roof)? We have done a very similar type of build but more DIY with material from different suppliers. I am big fan of ICF it would be interesting who jub are buying it from, it looks very similar izodom icf but that stuff is polish and jub stuff is Slovakian. 

 

Windows is a tricky one, a lot is down to the guy who is actually installing them! 

Edited September 17, 2018 by Alexphd1

[newhome]

Welcome! We are all very curious about other people's builds so it would be great if you could post some plans of what you intend to build. I think @PeterStarck used the Genvex 185 in his build. 

[Nickfromwales]

1 hour ago, Simon R said:

Hi and thank you to all forum members for creating a very useful resource.
Having managed to get planning permission my wife and I are about to start on our first self build. We intend to do as much work on the project as we can, we done several projects in the past but nothing on this scale
After a lot of looking at various build systems we have opted to use the JUB ICF sytem. Our intent is to get as low energy build as we can with our budget.
A little bit about the project: The house is in the region of 200M2 over two floors. The MVHR we are looking at the Genvex 185 unit which also gives us an integrated air source heat pump. We have not made a decision on windows yet but have Velfac on the short list.

Hi and welcome. 

Do some more maths with the 185 as I think you’ll struggle with it if you plan using it alone for space heating. 

The Genevex seems good at first glance, producing DHW as a biproduct of the mvhr doing its normal job, but remember that when you continuously remove heat energy from the extract air you don’t have anything left to put back into the house so you’ll be in deficit, particularly important in a house of ~200m2. 

Are you planning UFH or other space heating ? I’d really look at separating the two ( space heating and DHW ) as it’s much easier to tackle each individually imo. 

PV ? 

More info please !!

 

[Jeremy Harris]

8 hours ago, Nickfromwales said:

Hi and welcome. 

Do some more maths with the 185 as I think you’ll struggle with it if you plan using it alone for space heating. 

The Genevex seems good at first glance, producing DHW as a biproduct of the mvhr doing its normal job, but remember that when you continuously remove heat energy from the extract air you don’t have anything left to put back into the house so you’ll be in deficit, particularly important in a house of ~200m2. 

Are you planning UFH or other space heating ? I’d really look at separating the two ( space heating and DHW ) as it’s much easier to tackle each individually imo. 

PV ? 

More info please !!

 

 

The Genvex 185 removes heat for DHW from the exhaust air, not the extract air, so as much heat as is going to be recovered and returned to the incoming fresh air already has been.  The advantage is that the exhaust air from an MVHR will always be slightly warmer than the outside air, because the heat exchanger isn't 100% efficient.  The 185 allows more heat recovery from the house exhaust air, so increases the overall heat recovery efficiency.  The downside is really capacity.  It's a good unit for a passive house with a low heating requirement and relatively low DHW requirement, but in heat pump only mode for DHW it can be a bit slow to recharge the DHW if used in a house with a high DHW demand, I believe.  IIRC, there is a heating element included to allow direct electric water heating if a shorter  DHW re-heat time is needed.

 

[Triassic]

2 minutes ago, JSHarris said:

 

The Genvex 185 removes heat for DHW from the exhaust air, not the extract air, so as much heat as is going to be recovered and returned to the incoming fresh air already has been.

 

There can’t be much heat left in the exhaust air then?

[Jeremy Harris]

2 minutes ago, Triassic said:

There can’t be much heat left in the exhaust air then?

 

No, it's like our Genvex Premium 1L in that respect.  In heating mode the exhaust air can be very cold indeed, down around freezing or below, so the exhaust air duct needs insulating well to prevent condensation on the outside of it.

[PeterW]

6 minutes ago, Triassic said:

There can’t be much heat left in the exhaust air then?

 

Surprisingly yes..!!

 

Incoming air at 12c, exhaust at 5c after exchange is fairly common however as @JSHarris says, the trick is to get the heat out of it with a heat pump. Downside is with MVHR is that the flow is low - a standard Heat Pump will shift 50-70 cubic metres per minute through its coils, far more than an MVHR

[Nickfromwales]

4 minutes ago, Triassic said:

There can’t be much heat left in the exhaust air then?

Best effective in summer bypass mode, but if you've got PV you'll have DHW sorted anyway. Plus this is a bloody expensive bit of kit!! North of £8k iirc.  

In a PH I cant help thinking the money would be better spent on a stand alone MVHR system and separate DHW storage device. Get an MVHR with a small HP inside for summer cooling if thats a part of your remit. 

4 minutes ago, JSHarris said:

No

3 minutes ago, PeterW said:

Surprisingly yes..!!

Jesus, I'm only on my second cup of coffee and I'm already confused lol. 

[Simon R]

Good morning gentlemen. Just got to love this forum?, first post and already stirring the pot.

The house is low energy, and we are used to living off grid on a boat so tend to be carefully with our energy and water.

I'll start a thread in the ICF section to address the JUB aspects and other ICF items such as structural calculations and building controls. Incidently JUB tell me they are the manufacturer of the ICF.

Looking at sourcing the heat pump from Denmark as others on the forum have.

In the mean time, thank you all again for your interest and input. 

Simon

[PeterW]

@Nickfromwales to explain ...

 

- on a Genvex in heating mode ( a la @JSHarris) the heat pump element of it sucks as much heat as possible out of the exhaust air so it’s near freezing. 

 

- on an ordinary MVHR, the exhaust is ordinarily cooler than the input by a  few degrees however it’s flow is very low compared to a normal heat pump. 

 

Its the  reason the Genvex can’t put large quantities of heat into the air flow as it’s flow rate is so low. 

 

Clearer ..??

[Gone West]

Hi and welcome to the forum @Simon R. As has already been stated we have a Genvex Combi 185LS which provides the DHW and backup space heating. The LS version is the larger of the two types of Combi 185. Our main space heating is provided by an electric towel rail in each of the three bathrooms. This form of heating is only possible in our house because the space heating requirement is extremely low and the house is small. Unless you are planning to insulate your house to substantially higher levels than the minimum PH level I would use a different primary space heating method. Good luck with your project.

Edited September 18, 2018 by PeterStarck

[MikeSharp01]

1 hour ago, JSHarris said:

It's a good unit for a passive house with a low heating requirement and relatively low DHW requirement

Would the unit allow you to run the UFH from it assuming no other demands although the reversible cooling question then arises - assuming the unit has this feature and you could pump hot air out of the exhaust it might contend but in both modes power is likely to be a problem - have I got that right? 

 

We are going through the usual mill of deciding how to tackle the DHW side of things and had ruled out ASHP for DHW because of the infrastructure you need, losses associated and the availability of gas on site. ASHP for UFH looks like the chosen route. However we now find ourselves between a combi boiler just for DHW & maybe emergency UFH  and one of the many SUNAMP systems - so am looking forward to hearing the @JSHarris verdict on the latest incarnation.

[Nickfromwales]

55 minutes ago, PeterW said:

the heat pump element of it sucks as much heat as possible out of the exhaust air so it’s near freezing

It only does that until the DHW tank is fully charged. You then decide whether or not to continue using the HP for space heating. I've configured one of these to accept heat input from a pair of 9/58 eHeat ( SA TS's basically ) and thats input via the solar thermal coil in the 185 tank. All the time there's solar ( PV ) gain eg heat energy available from the SA's the 185 never kicks the HP in to recharge the DHW cylinder. The PV diversion device will also check in with the 1kW immersion in the 185 for overspill after the SA's are charged. That arrangement always sees that the 185 cylinder metabolism is healthy ( eg SA's don't provide DHW only heat transfer via primary water so the 185 can never stagnate ) and should leave the HP to be dedicated to space heating where necessary. 

1 hour ago, Simon R said:

Looking at sourcing the heat pump from Denmark as others on the forum have.

Ok, so as you want a HP are you having a slab and wet UFH as the primary means of providing space heating?

[Jeremy Harris]

4 hours ago, Nickfromwales said:

Jesus, I'm only on my second cup of coffee and I'm already confused lol. 

 

 

We're both saying the same thing, different use of terminology.  I was referring to the exhaust from the whole unit, not the internal exhaust between the MVHR heat exchanger and the heat pump heat exchanger, which is what @PeterW was referring to.  In the Genvex units there are two heat exchangers in series internally; the normal air-to-air MVHR one, then on the exhaust side of that there is the heat pump one.  The overall exhaust from the unit is what I was referring to as the exhaust, the air that actually gets exhausted out of the house via the exhaust air external terminal.

[Dreadnaught]

8 hours ago, PeterStarck said:

Unless you are planning to insulate your house to substantially higher levels than the minimum PH level I would use a different primary space heating method.

 

@PeterStarck When you said "higher levels than the minimum PH level" did you mean to say that or perhaps "higher levels than minimum building-regs' standard level", or some such, instead? I am planning to go to PH levels of insulation but not beyond. 

[Gone West]

5 minutes ago, Dreadnaught said:

 

@PeterStarck When you said "higher levels than the minimum PH level" did you mean to say that or perhaps "higher levels than minimum building-regs' standard level", or some such, instead? I am planning to go to PH levels of insulation but not beyond. 

I meant that the maximum U factor for PH walls, roof and ground floor is 0.15 w/m2K and that mine are 0.095 W/m2K which allows me to use the space heating system that we have.

[Simon R]

14 hours ago, PeterStarck said:

I meant that the maximum U factor for PH walls, roof and ground floor is 0.15 w/m2K and that mine are 0.095 W/m2K which allows me to use the space heating system that we have.

My rather rudimentary calcs have given me a whole house value of 51w/K, arrived at by totalling all areas * material U values. What I'm finding hard to evaluate is the solar gain we are going to get. I've modelled the house in sketchup to see the way the sun and shadows fall, it looks reasonably good in so far as we protect the windows from sun in the summer. It looks as though the 185 should do the job, but I'll revisit my calculations. 

We will have solar (PV) and intended to configure the unit only to heat when PV failed to heat the water. Also only intending a small area of wet underfloor heating, just 6m2. Lots still to figure out.

Edited September 19, 2018 by Simon R
error in value

[Gone West]

I used the PHPP to model our house which takes into account solar gain and also the residual heat gain from appliances etc. It might be worth getting a copy if serious about PH values.

[Simon R]

1 hour ago, PeterStarck said:

I used the PHPP to model our house which takes into account solar gain and also the residual heat gain from appliances etc. It might be worth getting a copy if serious about PH values.

Probably where we should have started. The 185 LS has capacity to spare even in the worst winter we are likely to get on the south coast, it's rarely below zero for more than a couple of days at a time in winter. Assuming the unit lasts 15 years, factoring in running costs it may just be simpler just to use PV and a couple of electrically heated towel rails. The RHI payments are not much of an incentive when you start getting close to passive house standards, at least that's my take on it.

[Gone West]

10 hours ago, Simon R said:

The 185 LS has capacity to spare even in the worst winter we are likely to get on the south coast, it's rarely below zero for more than a couple of days at a time in winter.

We had the electricity connected on 3/12/17 and started the Genvex Combi on the 19/12/17. We also had the electric towel rails on for eight hours a day at that time. We didn't move in until 3/4/18. Up until we moved in the temperature was around 22C. This coming winter will be the first full winter living in here so I will keep a record of what temperature we end up keep it at and our electricity usage.

[Jeremy Harris]

13 hours ago, Simon R said:

The RHI payments are not much of an incentive when you start getting close to passive house standards, at least that's my take on it.

 

Very true.  I worked out that the RHI payments on a heat pump installation for our passive house would have been around £84 a year for 7 years, not worth having given the premium price that an MCS approved installation adds to the overall cost.

[Simon R]

Just noticed I failed to respond to your post regarding Velfac. I would like to know what the issues were. Please would you add links/urls to the review you mentioned.

I know they have what is considered a low tolerance to variations in opening size, but other than that the quality and performance look good.