Insulation...do I need more?

[SuperJohnG]

I already know the answer to this question will likely be a resounding yes, even in my own head I think yes just get more for all the right reasons, it'll reduce the energy usage/ it's too hard to do later/ Later I'll wish I'd done it.

 

But - I've not currently planned to do it. 

 

SIPS kit with 169mm wall thickness, with 219mm thick Roof section. We have an insulated slab for reference

 

Current U Values:

 

 

I have been considering adding 50mm PIR internally on the walls and roof, I'm nervous that we will get in and I'll regret not adding it. This is somewhat driven by when the snow came a few weeks back I took the picture below. You can see the snow still solid on the canopy section, but right behind it melted quite quickly above a section which is my open plan area. Now the internals haven't even started so it will improve from there but you can see the difference with the snow melting there. 

 

So i am at a conundrum right now, I shoudl move inside in around a month, I've been at it a year already costs are above budget significantly (nothing horrific that I can't eventually afford) so hadn't allowed the costs or more importantly the time but also thinking I shoudl just suck it up and do it. 

 

I shoudl maybe look at the U value increase for the adding 50mm PIR then assess from there, cost will be around £4.5k plus VAT for the PIR (500 sqm). Or do I just focus on doing the airtightness aspect as this will make a more significant difference? as I am already a t a decent level of insulation in the SIPS kit. 

 

Bear in mind - I currently live in a 1975 thermalite block house with on ceiling insulation (done badly) and it's as leaky as a sieve. 

[Russell griffiths]

I would think looking at that pic, that you have a bad join at the ridge join, I would look if you have a solid timber up there, if so insulate that and get at it with airtight foam. 

 

[MikeGrahamT21]

Your u-values look good...if you've achieved them.

 

Check for gaps, airtightness and thermal bridging. £4.5k is a lot to spend when you've so much insulation already.

 

Also...did the other side of that roof melt in a similar manner? If not, it could just be the sun warming up the very dark tiles + a bit of heat leak, wouldn't take much to cause snow to slide on the smooth surface.

Edited February 1, 2022 by MikeGrahamT21

[SuperJohnG]

36 minutes ago, Russell griffiths said:

I would think looking at that pic, that you have a bad join at the ridge join, I would look if you have a solid timber up there, if so insulate that and get at it with airtight foam. 

 

Unfortunately I have a steel ridge beam that bridges the apex in between the panels - not a very good design. But I have planned to cover it internally with 50mm (more if I can) PIR foam around the edges. 

[LA3222]

Suck it up and get it done bud. I put 70mm on my walls and 75mm on the Ceilings just to get the 0.11 figures quoted by Kingspan Tek for SIP.

 

Electric is only going to get higher. If you're in this house for good, what will the Unit price of electric be in 30/40yrs time vs your outlay now? 

 

I also put the insulation inside as it will cover the studs/thick timbers within the wall and therefore reduce the bridging at these areas.

[SuperJohnG]

24 minutes ago, LA3222 said:

Suck it up and get it done bud. I put 70mm on my walls and 75mm on the Ceilings just to get the 0.11 figures quoted by Kingspan Tek for SIP.

 

Electric is only going to get higher. If you're in this house for good, what will the Unit price of electric be in 30/40yrs time vs your outlay now? 

 

I also put the insulation inside as it will cover the studs/thick timbers within the wall and therefore reduce the bridging at these areas.

Lol, I knew you'd say that. 

 

It's just so expensive, and I must have caught another £30k of unforeseen already which is painful. Did it take you long to do? 

 

I guess you just screw it on, tape it, VCL, then screw battens all the way through to the SIP panel?

[BenP]

Do it! 

 

It can't be done once you're in. The way we look at it on ours is that figures like that challenge our budget, but we aim to be there a long time and would rather leave rooms like en-suites unfinished. 

 

We've insulated over our timber frame with a complete layer of wood fibre and it is fantastically reassuring knowing there's very little in the way of cold bridging ?

[SuperJohnG]

2 hours ago, MikeGrahamT21 said:

Your u-values look good...if you've achieved them.

 

Check for gaps, airtightness and thermal bridging. £4.5k is a lot to spend when you've so much insulation already.

 

Also...did the other side of that roof melt in a similar manner? If not, it could just be the sun warming up the very dark tiles + a bit of heat leak, wouldn't take much to cause snow to slide on the smooth surface.

 

We haven't done the internals yet so still do sort gaps, airtightness etc. I can't remember about the other side actually, but this was the side with the sun. The other side does stay very cold as it never sees the sun in winter. 

 

15 minutes ago, BenP said:

We've insulated over our timber frame with a complete layer of wood fibre and it is fantastically reassuring knowing there's very little in the way of cold bridging ?

 

That is the bit I think I would like as it will remove all those cold bridges in the timber's in the roof panels and at points in the wall, albeit any joining ones are SIP splines in walls. 

[LA3222]

37 minutes ago, SuperJohnG said:

Lol, I knew you'd say that. 

 

It's just so expensive, and I must have caught another £30k of unforeseen already which is painful. Did it take you long to do? 

 

I guess you just screw it on, tape it, VCL, then screw battens all the way through to the SIP panel?

Yeah pretty much, it adds time and cost and cutting PIR is deffo a ball ache but once its done its done and you'll be happier for having done it. I just see electric going up a hell of a lot over the next couple of decades and it will pay for itself. Likewise I intend to smash solar at some point, anything to bring my future bills down. I'm all Electric so this transition to renewables is going to have a significant impact on my house energy costs. Such is life?‍♂️

 

As for the extra costs, happens to us all I think. I'm fast running out of cash, should get the house finished, probably nothing left to do the garden/garden room/garage/landscaping other than the VAT reclaim. Never gonna get all that done so will just do it as and when and learn to lay bricks myself?‍♂️

[Marvin]

If you are going to live in the building for a long time then the more insulation the better in my book, and by the look of the snow the more the merrier!!!!

 

Airtightness is also very important or a little more so in some ways. The cash flow is always a consideration.   My thoughts are if you need to find more money (or spend less) to complete the job the way you want, then defer works that won't cause you to redo works later.  I can live without an expensive kitchen for a while longer, or no garage if separate, or landscaping for example, But I want to be warm and dry with loos and showers that work with lower utility bills going forward.

 

We insulated and sealed against air flow and installed a MVHR system when renovating our 100m2 bungalow, and replaced the night storage heaters with a bottled gas fed boiler. (no mains gas) We toyed with the idea of PV but weren't convinced that the outlay was worth it. This all changed with the arrival of the electric vehicle and the option to have an ASHP also using electricity.

 

We now have what I think is the best combination of ASHP, MVHR, PV and EV. Would we have afforded all this at the time of building? No. However retro fitting some of the services through and airtight building has been a real pain. If you think you would fit anything later swot up on all the information on how to obtain the best from the proposed system and what the pitfalls are, and you may be able to prepare some of the things to avoid lengthy ( and costly) alterations later.

 

Good luck. 

 

M

 

 

[Iceverge]

You could forgo the PIR and batten out a service cavity with Rockwool or similar to insulate. 

 

More thickness but more bang for your buck.  Also better for fire and sound proofing. 

[Andehh]

I get the emotional desire to do more, but you'd never recoup that outlay in actual cost savings, even 20 years of living there! Insulation is a law of diminishing returns....

 

Your U values already put you into the top 1% of housing stock I'd bet. They are very good as is. 

 

Be very very sure there isn't a more tangible use for that money, one that reflects actual material benefit to you....solar panels? Mature tree planting? Quiet & covered seating area in the garden etc etc? 

 

 

[A_L]

8 hours ago, SuperJohnG said:

I have been considering adding 50mm PIR

 

This will reduce heatloss by about 2-2.5kWh/m²/yr, so the question is, how much will it (cumulatively) cost to put 2-2.5kWh of heat into the heated space?

[SuperJohnG]

3 hours ago, Andehh said:

Be very very sure there isn't a more tangible use for that money, one that reflects actual material benefit to you....solar panels? Mature tree planting? Quiet & covered seating area in the garden etc etc? 

 

I'd have liked solar panels, but couldn't make the maths over at 2.5k for them and was stuck for time. Most other things above are covered already. But makes sense to look at other areas. 

2 hours ago, A_L said:

 

This will reduce heatloss by about 2-2.5kWh/m²/yr, so the question is, how much will it (cumulatively) cost to put 2-2.5kWh of heat into the heated space?

 

Thats the sort of info I'm looking for, so can I just base that on the surface area?  Then pro rata a cost for the electricity?  

4 hours ago, Iceverge said:

You could forgo the PIR and batten out a service cavity with Rockwool or similar to insulate. 

 

More thickness but more bang for your buck.  Also better for fire and sound proofing. 

Thats seems even harder. Woukd be much more work doing thus over a sip panel with deeper studs unfortunately. Their will be a service void above whatever the final internal layer is. 

[A_L]

11 hours ago, SuperJohnG said:

Thats the sort of info I'm looking for, so can I just base that on the surface area?  Then pro rata a cost for the electricity?  

Yes, plus your view on energy price inflation ?

[SuperJohnG]

21 minutes ago, A_L said:

Yes, plus your view on energy price inflation ?

Thanks, 

 

very basic calcs based on 17p/kWh at the moment gives the following costs over 20 years, based on %  energy price rises per year:

 

Edited February 2, 2022 by SuperJohnG

[Nickfromwales]

11 hours ago, SuperJohnG said:

I'd have liked solar panels, but couldn't make the maths over at 2.5k for them and was stuck for time

With a typical 4kwp array consuming around 26-28m2, and an assumed cost of £100p/m2 for supply and fit of slates, you'd have had a hypothetical credit note of north of £2.5k from the roof costs savings with an in-roof array. Shame, as that roof was crying out for PV. £30k of uplift must be a bitter pill though, so spend wisely from  here on-in.

FWIW, I would go 75mm additional on the under-roof ceilings and 30mm on the walls, if on the walls at all tbh. Heat rises, and your walls are not too shabby now!

In absolute honesty, if you have ~£5k sat on the desk wanting spending, and the scaffolding is still up, I'd get the slate ripper out and put a PV system in without a second thought.

I would definitely NOT be getting hung up on the heat loss "horrors" that you are mentioning above, just based on seeing some snow melting. Get the steel beam boxed in 50-75mm minimum of PIR, sealed with illbruck air-seal foam, no voids left whatsoever, and EVERY bit of your airtightness detailing done, and THEN reassess. You'll have little to none of the issues you are seeing now if the heat isn't rising and escaping without any real resistance, so you've basically got a chimney there atm until AT works have been done. 

[Nickfromwales]

2 minutes ago, SuperJohnG said:

Thanks, 

 

very basic calcs based on 17p/kWh at the moment gives the following costs over 20 years, based on %  energy price rises per year:

 

Budget for midnight to midnight at 30p/kWh. That's the likelihood, and how I'm basing all my current proposals.

A/C coupled battery systems will soon be boat anchors all winter long, especially when they bottom out and want some charge from the grid.

[SuperJohnG]

4 minutes ago, Nickfromwales said:

With a typical 4kwp array consuming around 26-28m2, and an assumed cost of £100p/m2 for supply and fit of slates, you'd have had a hypothetical credit note of north of £2.5k from the roof costs savings with an in-roof array. Shame, as that roof was crying out for PV. £30k of uplift must be a bitter pill though, so spend wisely from  here on-in.

 

 

In absolute honesty, if you have ~£5k sat on the desk wanting spending, and the scaffolding is still up, I'd get the slate ripper out and put a PV system in without a second thought.

I would definitely NOT be getting hung up on the heat loss "horrors" that you are mentioning above, just based on seeing some snow melting. Get the steel beam boxed in 50-75mm minimum of PIR, sealed with illbruck air-seal foam, no voids left whatsoever, and EVERY bit of your airtightness detailing done, and THEN reassess. You'll have little to none of the issues you are seeing now if the heat isn't rising and escaping without any real resistance, so you've basically got a chimney there atm until AT works have been done. 

I did want to do it, but unfortunately we had major issues with the roof getting fitted and generally the workmanship from the suppliers subcontract team - which basically burnt all my time at the point. I'd worked out at that point (I was around 65/m2 for supply and fit of slates) that it might only cost me £1000 but there was too much going on and I didn't have the time to work out what needed done, coordinate it with the roofers and get it sorted. The only option was to hand it to a company to do - but they wanted north of 8k to supply and fit panels and I knew I could get them supplied for £2.5k. All a shame really. 

 

I don't think I could fathom ripping the slates up just now - just so hard to plan and redo.  

 

Boxing the beam and good attention to airtightness all planned, the point around doing ceilings only might lessen the blow and be a good shout.  

 

[SuperJohnG]

9 minutes ago, Nickfromwales said:

Budget for midnight to midnight at 30p/kWh. That's the likelihood, and how I'm basing all my current proposals.

A/C coupled battery systems will soon be boat anchors all winter long, especially when they bottom out and want some charge from the grid.

30p? why midnight onwards? 

Is this foreseeing batteries as a no use during winter? due to high costs to charge now?  

[LA3222]

35 minutes ago, Nickfromwales said:

Budget for midnight to midnight at 30p/kWh. That's the likelihood, and how I'm basing all my current proposals.

A/C coupled battery systems will soon be boat anchors all winter long, especially when they bottom out and want some charge from the grid.

30p...absolutely...long term Electric costs are going to rise sharpish. Its one thing I could never understand on this forum, all the naysayers for PV couldn't make it work financially - that's true if you work under the mental assumption that prices would remain static. I always said they will inevitably rise so think holistically about long term implications. I never thought they'd rise this quick though - I'm at 19p per kWh - I reckon that will.be closer to 25p in a year or two. If Russia kick off then it will be 25p a lot quicker than anyone wants or thinks!

[SuperJohnG]

8 minutes ago, LA3222 said:

30p...absolutely...long term Electric costs are going to rise sharpish. Its one thing I could never understand on this forum, all the naysayers for PV couldn't make it work financially - that's true if you work under the mental assumption that prices would remain static. I always said they will inevitably rise so think holistically about long term implications. I never thought they'd rise this quick though - I'm at 19p per kWh - I reckon that will.be closer to 25p in a year or two. If Russia kick off then it will be 25p a lot quicker than anyone wants or thinks!

Definitely a missed opportunity, which I feel a bit sad about but such is life. I do have lots and lots of space and planning a big shed up the back so that might be the saving grace to stick it up there. 

[Nickfromwales]

7 minutes ago, SuperJohnG said:

30p? why midnight onwards? 

Is this foreseeing batteries as a no use during winter? due to high costs to charge now?  

Midnight to midnight eg 24/7/365.

 

30p? It's most definitely where the consumer market is heading for the purchase price of domestic electricity. Sadly, in 3-5 years we'll likely be north of 35p/unit, or above. Look at fuel prices at the pump.....they push, we smile ( through helpless gritted teeth ), and just pay. Pending huge costs for improvements and fortification of the grid has to come from somewhere, and guess where that cost will be pointed at? Elderly and poorer folk look out.  

 

Solar PV.........."Fail to prepare, prepare to fail". We all use electricity in considerable quantities, we all have roofs. Most are suitable for the installation of at least 1kWp of self fit ( via electrician ) PV which will serve us well whilst we are in work paying for the rest of what we use. Calculate the vampire / daytime base-loads that are happening whilst the house is vacated each day, and aim for that as a minimum. Remember that an electrician can assist you in DIY'ing a grid-tied PV system, but without MCS accreditation you CANNOT claim the export payments of ~5.2p/unit  .  If just installing enough to cover base loads, then no need for MCS as you would be pretty much a self-consumer and theres nothing stopping you diverting any excess into an immersion heater to bolster DHW etc ergo you would not care about not getting the export payments and can then save on any unnecessary elevations to the capital cost of such an installation. DIY all the way then!!

 

Regarding A/C batteries? Deffo. People who already have larger sized ( 7.2kWh and above ) grid-hungry A/C coupled batteries will literally be disconnecting them when they become faced with no cheap rate overnight grid power to make up the winter deficit. Options then would be to manually 'tend to their winter needs' by maintaining the state of charge and cycling simply to preserve the cell life for those generation shy periods of the year. They still make sense inn summer, but winter is about to get extra chilly in the respects of A/C storage ( essentially named so as it is supposed to store excess and not be fed from the grid, due to the then nonsensical economics of cost vs lifespan and losses of throughput ). 

 

Solar PV revenue is around 25-30% max over the depths of winter, and we're already not in the sunniest country in the world to start with, so prepare yourselves for this flat rate AFAIC. Assuming batteries will charge from anything other than grid during winter, especially for retiree's / folk who work from home eg savvy users with larger self-consumption figures, there will be zip left to go into them. D/C will be the way forward then, and I am awaiting Solarwatt to return their D/C offering back to the domestic market, new and improved, before I then invest myself ( as they are rated and guaranteed to 'hiberante at their lowest DoD for long periods of time ). PV on mine next year hopefully, batteries to follow as and when. 

 

We digress......

 

anyways......when has that ever stopped us  

 

5 minutes ago, SuperJohnG said:

Definitely a missed opportunity, which I feel a bit sad about but such is life. I do have lots and lots of space and planning a big shed up the back so that might be the saving grace to stick it up there. 

Then go for that after the dust has settled. Install enough to cover the daily base loads, as I describe above, and then at least you remove the daily grind from your electricity usage with minimum capital expenditure. A colleague installed 4x 250w second hand panels on his roof, and I was seriously impressed with what they were chucking out each day. Really put a dent in his daily import.

 

[Nickfromwales]

12 minutes ago, SuperJohnG said:

Definitely a missed opportunity, which I feel a bit sad about but such is life. I do have lots and lots of space and planning a big shed up the back so that might be the saving grace to stick it up there. 

Don't forget ducts for cables, if not already in  A more modest sized array could just feed into the shed CU. Size the SWA accordingly. 

[Nickfromwales]

24 minutes ago, LA3222 said:

all the naysayers for PV couldn't make it work financially

We're already in talks with Mr Kipling, to manage the expected rise in demand for humble pie.......