Novice Help

[richo106]

Hi All

 

We are planning our renovation project for this year, our village doesn't have mains gas

 

We think we have decided to go for ASHP (16.5kw Daikin Altherma) to supply our heating/DHW..so solely electric rather than LPG or Oil

 

The way our house faces, with very small section south facing and blocked by tree so I don't think it will be very suitable for solar panels (see picture)

 

Would people still look into solar panel and maybe have a company come round before ruling it out?

 

Is there any other options to help reduce energy costs? I'm guessing only battery storage is useful when having some solar panels (or another form of generation)

 

All advice and information appreciated

 

Many Thanks

[JohnMo]

What about a ground array at the end of the garden?  With optimisers on each panel to limit the effects of shading.

 

PV with an immersion diverter, to use excess generated electric to make hot water.

 

Battery storage expensive.

 

Before any of the above look at insulation, draft and air leakage. That's the best money spent.  Before you go to a heat pump, you need a house that can operate on low temperature heating, otherwise running costs will be high.

[ProDave]

That picture looks to be rotated, i.e. south up, unless you are in the southern hemisphere.

 

How about a ground mounted PV system at the southern end of your garden?  Then make it into a shed:

 

[richo106]

36 minutes ago, JohnMo said:

What about a ground array at the end of the garden?  With optimisers on each panel to limit the effects of shading.

 

PV with an immersion diverter, to use excess generated electric to make hot water.

 

Battery storage expensive.

 

Before any of the above look at insulation, draft and air leakage. That's the best money spent.  Before you go to a heat pump, you need a house that can operate on low temperature heating, otherwise running costs will be high.

Thanks for the reply 

 

Regarding insulation, there will be 150mm under the UFH in our new ground floor slab, the existing building has 70-80mm cavity with insulation in and I will be insulating internally using either 50mm PIR or rock wool depending on what system we install (recommendations welcome!)

also in the bedrooms with vaulted ceilings will be 100mm PIR between the joists.

 

windows are residence 7

 

You mentioned air tightness, what are the best ways to achieve this? 

we want a couple of log burners in kitchen/diner and lounge…are these Ok for air tightness? 

Many Thanks 

[JohnMo]

Once you less than 3 ACH you need to add additional ventilation I believe, our wood burner is ventilated directly through the wall so does not use house air.  Which doesn't need additional ventilation.

 

You can get a diagnosis air test for about £200, which will depressurise the house and can then go around the house and feel where you have leaks.  Another way would be put on your extract fans and go around with a candle or similar and watch when the flame moves, by doors, windows, sockets etc.  Make list go around an repair/ draft proof etc.

[Nickfromwales]

After 9m2, iirc, you need planning permission for a ground mounted array. A great option if feasible, and we’ve done a few with great results. If the trees can’t go, your options are significantly reduced there. Also remember that PV will never offset or aid heating in winter unless you’ve a monster of an array ( impossible to get on single phase ). 

Can you get another 50mm of EPS insulation under the 150mm of PIR? Will be a better result and you can lay your DPM atop the EPS to keep it free from punctures. 
The 100mm between rafters is good, but also consider installing 25-40mm of full sheet PIR over the rafters to give you greater results by arresting the cold bridging from where the plasterboard meets the rafters. Pre-insulated plasterboard is a perfectly good option there, but I prefer to separate the two and stagger the joints. 
The same pre-insulted boards can be used to form your IWI also, ‘stuck’ with dot and dab but with a continuous bead of dab or expanding foam to stop thermal tenting.

 

[richo106]

19 minutes ago, Nickfromwales said:

After 9m2, iirc, you need planning permission for a ground mounted array. A great option if feasible, and we’ve done a few with great results. If the trees can’t go, your options are significantly reduced there. Also remember that PV will never offset or aid heating in winter unless you’ve a monster of an array ( impossible to get on single phase ). 

Can you get another 50mm of EPS insulation under the 150mm of PIR? Will be a better result and you can lay your DPM atop the EPS to keep it free from punctures. 
The 100mm between rafters is good, but also consider installing 25-40mm of full sheet PIR over the rafters to give you greater results by arresting the cold bridging from where the plasterboard meets the rafters. Pre-insulated plasterboard is a perfectly good option there, but I prefer to separate the two and stagger the joints. 
The same pre-insulted boards can be used to form your IWI also, ‘stuck’ with dot and dab but with a continuous bead of dab or expanding foam to stop thermal tenting.

 

I can definitely mention the 200mm PIR instead of the 150mm originally the building said 100mm but I upped him to 150.

 

good idea regarding the additional PIR in the vaulted ceiling bedrooms I will be definitely be doing that.

 

Regarding the insulated backed plasterboard, do you think this will give better performance than say a stud wall infront of the walls with an 10mm air gap and 50mm rock wool insulation?

 

thanks again 

[Nickfromwales]

1 minute ago, richo106 said:

Regarding the insulated backed plasterboard, do you think this will give better performance than say a stud wall infront of the walls with an 10mm air gap and 50mm rock wool insulation?

Difficult to say definitively, unless more dialogue over specifics follows, but certainly it would be more compact a solution and therefore less impactful to the available internal floor space. An air gap is not your friend, unless you have detailed the joints and perimeters meticulously, as the aforementioned “thermal testing” becomes something to rob you of all your hard work, and even cancel It out in extreme cases! 

[Nickfromwales]

Check out some of @nod’s posts on dot snd dab methods where continuous beads are formed by closely applying the ‘dabs’ ( which then all meet when the board is dabbed onto it ). 
Lots of great info on here, but the problem is that the conte t level here is huge so perseverance will be required. 

[Nickfromwales]

 

[richo106]

Thank you, I will look into them

 

What about the warm wall method?

50mm PIR, then 25mm studs with a fixing through the battens and PIR? What fixings would be best to fix through them both? 
 

Would I then install cables and pipe work the warm/room side? In the 25mm void?

 

Thanks again 

 

[Nickfromwales]

Cable behind on the bare walls, prior to the boards / IWI going on   Negates a service void and unwanted extra depth. 
Dab is fine over the cables, but they cannot be in continuous runs of foam as that is insulation and would require down rating of the circuits / upsizing of the cables. 
Back boxes can be parged around and dabbed whilst boarding to mitigate infiltration. 

Edited January 12, 2022 by Nickfromwales

[richo106]

8 hours ago, Nickfromwales said:

Cable behind on the bare walls, prior to the boards / IWI going on   Negates a service void and unwanted extra depth. 
Dab is fine over the cables, but they cannot be in continuous runs of foam as that is insulation and would require down rating of the circuits / upsizing of the cables. 
Back boxes can be parged around and dabbed whilst boarding to mitigate infiltration. 

I've been looking into PIR backed plasterboard, seems very expensive. Suppose would save on labour costs

I was looking to do stud walls/partitions/battens myself just I wouldn't fancy dotting and dabbing on that large of scales

 

Downstairs I will be insulating over existing plaster...is it best to take all this off? before I insulate internally

 

Many Thanks

 

[Nickfromwales]

By the time you’ve paid for materials and lost much more internal space, the insulated boards soon appear much cheaper eg better value for money ( imho ). 
A good dabber ( +1 labourer ) will put a lot of sheets on in one day, so you can economise on that cost by making sure materials are to hand, be there to clean up as the guys are working etc. 
I would only stud if a BCO had spec’d 75 or 100mm , but up to 50/60mm I’d be dabbing for sure. 

[richo106]

1 minute ago, Nickfromwales said:

By the time you’ve paid for materials and lost much more internal space, the insulated boards soon appear much cheaper eg better value for money ( imho ). 
A good dabber ( +1 labourer ) will put a lot of sheets on in one day, so you can economise on that cost by making sure materials are to hand, be there to clean up as the guys are working etc. 
I would only stud if a BCO had spec’d 75 or 100mm , but up to 50/60mm I’d be dabbing for sure. 

Thanks Nick, another speedy and very useful response

 

Many Thanks

[richo106]

I will try to avoid installing sockets in the external walls where I will installing the PIR backed board, but in some cases this can't be avoided.

 

What's the best way to install sockets/switches when using 50mm backed boards?

 

I will also be installing kitchen units on a external wall, what would be the best way for this? I was thinking of installing osb behind the PB but what would be the best way to do this now?

 

Sorry for all the questions, as you can tell its my first time using these products

 

Thanks again

[Nickfromwales]

Don’t avoid sockets, just create a robust method to install, so as to reduced / eliminate infiltration, and put as many in as you like. 
Use fast fix boxes Link and just feed the cables through 30mm holes dead centre of each socket box location. Then you use a pad saw / other to cut out ONLY the amount of depth you need, through the PB and into the PIR. Allow an extra 5mm of depth for foam to expand into.
Once the wall is prepped for the fast fix box to be installed you can use a blank module plate  Link as a dummy socket face so as to be able to temporarily fit the 2x plate screws and tighten up the fast fix box ‘wings’ and then level off with a small boat level. Fast fix boxes are loose until the plates are fitted and the plate screws fully tightened   

Then you can use a foam gun to fill the cavity at the sides / rear and the hole the cable comes through for a bombproof install. Use air block foam such as Illbruck pro Link and that will also create a very good mechanical fix too as it cures significantly firmer than builders / typucal

expanding foam.

 

The OSB method is a no brainer, it just means fitting regular PIR sheets, then OSB over those, with long screws through for extra purchase where you predict there will be known loads affixed to it later, then the PB ( in each critical area ). 

[AliG]

Thanks for linking my thread @Nickfromwales

 

I dod think that the PIR boards on the external walls work well.

 

Main recommendation I would reiterate for dot and dab is to seal around the edges of the boards to stop air moving around behind them. This is particularly important at the top and bottom as otherwise cold air will come out into the ceiling void and below the skirting boards.

 

I think the correct way to do it is to create a full edge of dab on the boards, but it may be more practical to simply foam the edges once they are up. I just did this around my garage ceiling as I was suspicious cold air could get into the house from the garage via the edges of the board and it took minutes with a foam gun. Ideally I would have done this everywhere in the house.

 

Do not remove the plaster from the walls if it is sound as this will improve air tightness behind the boards.

 

Another important area is the window reveals. Make sure the edges of the windows are well sealed before the plasterboard goes on. As well as air infiltration it makes a big difference to outside noise.

 

It sounds like inside walls are stud walls. I would avoid dot and dab on interior walls. The main reason is that it is poor for sound transmission between rooms. For all walls I do think it should be standard practice to seal the edges to stop flanking sound between walls. It is included in some details for sound transmission but exactly the kind of works builders think isn't necessary. It is not even time consuming or difficult.