SAP fail mainly due to walls

[Gus Potter]

1 minute ago, WWilts said:

Yes, basic cavity wall was the original design. Failed SAP. Interested in improving energy efficiency in reasonably cost-effective ways, anyhow. For SAP and otherwise too.

Hello WWilts.

 

Sorry if I laid it on a bit thick there. You could look at timber frame. Design is an iterative process.. (I  paraphrase - there are a number of better qualified members than I on BH)   you start by listening to a Client's requirements, understand how they want to live now and in the future. A good designer will do a bit of "gaming".. what if you have more kids, what if  you need to change jobs and want work from home etc, what are your aspirations.. energy use.. ( to use a cliche). Now as a designer you have an incling as to what the "soft" requirements are.

 

To make this work within a budget it starts under the ground. It may seem a bit odd but if you go for the simple stupid option this can really knock a lot off the builder's price as the tender field is more open for example. I often think and see that folk have spent a lot of money on structure (and associated foundations / labour cost)  creating a daft open span, or just the wrong span.

 

Get the basics nailed early then you can then use this saving to upgrade insulation etc and also spend some money on.. heating controls/ rainfall showers and so on, some Farrow and Ball paint, stuff which you get to have fun playing with and can see every day. Remember that a house is not just to keep the weather out and you warm.. there is value in being able to play with it , adjust stuff up and down. Visitors only see the finished result.. not the insulation. There is no harm in showing what you have achieved.

 

Wilts it may take a bit of work but go back and review from the foundations up and you may get a pleasant surprise.

 

 

[PeterW]

6 hours ago, WWilts said:

That's an angle not considered before. Quickly reaching weathertight stage was incentive for thin joint blockwork. Perhaps it's a bad idea?

 

You will be slower with thin joint and brick. 
 

1. Thin joint uses glue, bricks use mortar. Your brickies will need to alternate between the two, and can’t “use up the last of the mix” on 15 blocks at the end of the day. 
2. Wall ties take seconds to place and are cheap. Start using helical ties and you’re needing the tools plus they take time to install. They are about 10 times the price of standard ties too. Most BMs don’t stock thin joint glue so when you run out it’s another delay. 

3. Labour doesn’t know what thin joint is in the UK. Expect a lot of waste, broken blocks and excessive use of materials - they are learning on your job and will be slow to start with. Coursing will need to be accurately managed, as will lintel placement. 

4. Contractors price what they know. How many bricks and blocks they can lay in a day. They can do those calculations on the back of a Greggs bag ... new stuff they will guesstimate then add 20% for hassle factor. 
 

Thin joint isn’t your answer here ..!

[epsilonGreedy]

8 hours ago, PeterW said:

100mm can no longer pass unless you use insulated plasterboard - your architect should know that. 
 

 

I know of one new build with standard cavities that passed in 2019 with a mid C EPC score.

 

I will be using insulated plasterboard BTW.

[Gus Potter]

Thanks Peter.. I think you have forgotten more than I know, as have many members on BH.

 

 

 

 

[WWilts]

1 hour ago, PeterW said:

Thin joint uses glue, bricks use mortar. Your brickies will need to alternate between the two, and can’t “use up the last of the mix” on 15 blocks at the end of the day. 
2. Wall ties take seconds to place and are cheap. Start using helical ties and you’re needing the tools plus they take time to install.

Main incentive is short time to weathertight. Then it's less daunting to self-manage this alongside many other commitments.

Plus outer leaf blocks can boost the energy efficiency of the wall relative to brick or stone, I believe. Is that mistaken? 
 

Edited January 30, 2021 by WWilts

[PeterW]

9 hours ago, WWilts said:

Main incentive is short time to weathertight. Then it's less daunting to self-manage this alongside many other commitments.

Plus outer leaf blocks can boost the energy efficiency of the wall relative to brick or stone, I believe. Is that mistaken? 
 

It will be slower. If you want quick to watertight then timber frame is your choice. 
 

What is the driving the desire to get to a fast watertight shell..? This is pretty much where the cost / time / scope equation comes in - if you want quick and the same scope or quality then it will cost more. 
 

In terms of outer leaves, the range is from around 0.4 at the aerated block level to 1.6 for concrete heavy blocks, with bricks sitting somewhere in the middle around 0.8-1. 
 

Now consider that your insulation has values of a tenth of that lowest level, and you can see that actually unless you go for a super light - and expensive - block you will be shaving less than tenths off the wall value.  What you need to do is increase the ratio of the upper and lower values so increase your insulation layer as a proportion of the wall build up. 
 

The average house (140sqm box)  has three layers of insulation. A 70sqm floor, a 70sqm attic, and around 150sqm of wall. The insulation cost of the wall insulation at 100mm is around £550, the cost of it at 125mm is £630, at 150mm is £770. So if you factor in a slight increase in cost of lintels and ties, it is probably circa £500 on the cost of the materials. For a building that now has a significantly better uValue for its walls and will more than reach your SAP score. 
 

You can’t get the renewables to do the same for less than £2k I expect and you will not recover the additional cost through any sort of FiT or self usage in 5 years. 
 

 

[WWilts]

6 hours ago, PeterW said:

The average house (140sqm box)  has three layers of insulation. A 70sqm floor, a 70sqm attic, and around 150sqm of wall. The insulation cost of the wall insulation at 100mm is around £550, the cost of it at 125mm is £630, at 150mm is £770. So if you factor in a slight increase in cost of lintels and ties, it is probably circa £500 on the cost of the materials. For a building that now has a significantly better uValue for its walls and will more than reach your SAP score. 

Very helpful. Thanks

[SteamyTea]

On 29/01/2021 at 16:12, ProDave said:

No mention of renewables like solar PV?

Yes,  look at the cost of fitting roof integrated PV.  It can be cheaper than tiling.

[WWilts]

5 hours ago, SteamyTea said:

Yes,  look at the cost of fitting roof integrated PV.  It can be cheaper than tiling.

Very helpul, thanks

[epsilonGreedy]

On 31/01/2021 at 10:45, SteamyTea said:

Yes,  look at the cost of fitting roof integrated PV.  It can be cheaper than tiling.

 

 

I have read this before on BuildHub but the numbers don't add up.

[SteamyTea]

4 minutes ago, epsilonGreedy said:

 

I have read this before on BuildHub but the numbers don't add up.

They never do for you, but that is because numbers are for the feeble minded and are just made up.

You have to pick the right system components, not the most expensive tile replacement types.

[epsilonGreedy]

11 minutes ago, SteamyTea said:

They never do for you, but that is because numbers are for the feeble minded and are just made up.

You have to pick the right system components, not the most expensive tile replacement types.

 

 

Take an expensive slated roof at say £2 per slate, £1 per tile to fix and 20 slates per m2 = £60 per m2.

 

Now I will leave it up to you to present the alternative integrated PV costs including the special inline under trays, extra flashing and slate fitting around the trays.

 

I think integrated roof PV is a great idea but roof cover cost saving is not a motivation.

Edited February 1, 2021 by epsilonGreedy

[joe90]

18 minutes ago, epsilonGreedy said:

 

I have read this before on BuildHub but the numbers don't add up.

It did fir Jeremy!!!

[epsilonGreedy]

2 minutes ago, joe90 said:

It did fir Jeremy!!!

 

 

Someone on BuildHub has claimed that and it might have been Jeremy, but the costs simply do not support the claim by a large margin.

 

Just go and research the per m2 material costs before factoring labour. How much does PV costs per m2, then add in the fancy inline under panel trays.  

[SteamyTea]

https://improvementcosts.com/costs/roofing/home-roofing-cost/

 

Are you using Phillips Moss as your builder.

[epsilonGreedy]

5 minutes ago, SteamyTea said:

https://improvementcosts.com/costs/roofing/home-roofing-cost/

 

Are you using Phillips Moss as your builder.

 

 

Your table indicates £85 per m2 for a whole roof which is good and close to my slate roof costs. After obtaining that quote @ £85 per m2 ask the the same roofer how much can be saved by putting in 4 Kw of in-line solar including the costs of the actual panels and watch him walk away laughing.

[epsilonGreedy]

28 minutes ago, joe90 said:

It did fir Jeremy!!!

 

 

I think the confusion arises because some interpret Jeremy's claim to mean substituting 3 m2 of slated roof with 3 m2 of integrated PV lowers the overall roof cost. What Jeremy might have been saying is that integrated PV is not a more expensive option for fitting expensive PV panels compared to fitting panels on top. Even this claim is a bit dubious when the material costs of the under tray system plus labour is considered.

[Bitpipe]

1 minute ago, epsilonGreedy said:

 

I have read this before on BuildHub but the numbers don't add up.

 

I suppose it depends on the cost of the planned roof covering - Jeremy used a recycled plastic slate, but I agree that 'cheaper than' is a stretch.

 

However, if you use an in roof tray system then you can obviously subtract the cost of roof covering in the area where PV is installed from the overall PV budget. 

[epsilonGreedy]

3 minutes ago, Bitpipe said:

I suppose it depends on the cost of the planned roof covering - Jeremy used a recycled plastic slate, but I agree that 'cheaper than' is a stretch.

 

 

Natural slate typically ranks as one of the more expensive roof covers, which is why I used it for comparison. Even if the cost of the PV panels is excluded from the calculation and we just compare the integrated mounting system/trays to a few meters of fitted slate mid roof, I do not think the claim is true.

 

I only posted today because I read the original claim on this forum 2 years ago and at the time thought "wonderful, I can fit a few m2 of integrated PV and still lower my over all roof costs". After spending a few hours online I concluded that just the integrated mounting system costs a little more than the equivalent area of finished slate roof. Now that I understand where the money and labour goes in a roof, I suspect the differential is a bit larger.

 

I think integrated PV is an excellent idea and I hope that once the mounting systems loose their leading edge price premium and general roofers can quote for the added fitting complexity, then the system will become a lot more popular.

[PeterW]

14 minutes ago, epsilonGreedy said:

After spending a few hours online I concluded that just the integrated mounting system costs a little more than the equivalent area of finished slate roof.

Really ..?? 
 

Count all your double battens etc for the slates, and take a broad brush of £75/m for material and labour for a slate roof. Then look at the cost of the systems and you’re probably looking at around £40/m to purchase and I would expect around £15/m to install. That’s a £20/m saving, and you have a system ready to receive the panels. For a standard 14 panel install, and panels at ~£100 each, your saving pays for 5 panels so you’re at net benefit with using the system with PV (if required for SAP). 
 

[epsilonGreedy]

11 minutes ago, PeterW said:

Really ..?? 
 

 

Yes???

 

11 minutes ago, PeterW said:

Then look at the cost of the systems and you’re probably looking at around £40/m to purchase and I would expect around £15/m to install.

 

 

Can you provide a link? GSE is the main low-end option and the material cost is £100 a mounting panel including ancillaries for guess (guess) 1/3 m2. Labour cost for trimming tiles around that plus flashing will be more than running through with an already gauged pattern of slate.

 

[dpmiller]

IIRC the GSE trays are not much over £30 each, the hold-downs and tekscrews a couple of quid each, and the flashing is worked out per perimeter. And a panel is about 1.5m2... The only other thing you need is some 4x1 to screw down onto in the right zones.

[PeterW]

29 minutes ago, epsilonGreedy said:

 

Yes???

 

 

Can you provide a link? GSE is the main low-end option and the material cost is £100 a mounting panel including ancillaries for guess (guess) 1/3 m2. Labour cost for trimming tiles around that plus flashing will be more than running through with an already gauged pattern of slate.

 

Search for a quote by @canalsiderenovation on the forum as the costs for the panels are on that but it’s about £30-40 for the trays. 

[pdf27]

3 hours ago, epsilonGreedy said:

Can you provide a link? GSE is the main low-end option and the material cost is £100 a mounting panel including ancillaries for guess (guess) 1/3 m2. Labour cost for trimming tiles around that plus flashing will be more than running through with an already gauged pattern of slate.

https://midsummerwholesale.co.uk/buy/roof-integrated-solar-pv - £33 exc VAT, before any discount.

It **just** gets to £100 a panel if you are only fitting a single panel and using the GSE flashings all around - as soon as you put in a big block the cost comes right down.

Edited February 1, 2021 by pdf27
Comment on flashings

[Iceverge]

I'm a bit sceptical of build in panels. 

 

Will replacement parts of the same size be in available in 30 years or sooner if the panels fail? The more holes and fiddling and flashing you do with the roof the more likely it is to leak. Maybe not tomorrow but some day. 

 

With that in mind our PV is going on the garage and there's not a single penetration or hole in our hip roof. No lead no joints no nothing. Paranoid maybe!!