Render, EWI and DPC - Advice needed

[canalsiderenovation]

We should hopefully getting our EWI and render in the next couple of weeks thank the bl00dy heating gods because we are hoping this will improve the bills!

 

You'll know from the original layout of our bungalow that part of the bungalow is stepped inside (to the bedroom/dressing room) as it is higher. This means the DPC is at a different level. This is going to look really odd as we have our DPC at different levels. The builder was speaking to the different reps about the render and if there was any solution because it's going to look a bit messy with the render coming lower on some parts and higher on others. It's days like today when I wish we would have knocked the whole thing down......

 

Pic below is our bedroom and dressing room and the bungalow is higher here as we step up two steps to access this part of the bungalow.

 

 

This pic below probably demonstrates it better and you can see how it steps up. The scaffolding is in front of the living room/snug and the wall window is the middle hall. Ignore the garden walls and any paving etc... 

 

 

And then this is close to our front door where we have the existing part on the left which is pretty much where it is stepped inside and then our extension.

 

 

We had picked Krend pure white but I've just had an email from the builder with the spec for the EWl and render and it's something called Ecorend and Jablite. Is Ecorend similar to Krend? 

 

And Jablite - is this a suitable EWI?

 

Feeling slightly overwhelmed again!

 

EcoRend_Spec.pdf Jablite Spec.pdf

[PeterW]

What’s the thickness of insulation and what was the spec on the designs / BRegs..?

 

Ecorend is a through colour render - @nod any feedback ..?

[canalsiderenovation]

10 minutes ago, PeterW said:

What’s the thickness of insulation and what was the spec on the designs / BRegs..?

 

Ecorend is a through colour render - @nod any feedback ..?

 

50mm EWI

[PeterW]

Ok did it not say product type as 50mm EPS / PIR / PUR will have different uValues so that should be stated on the BRegs design as it affects the SAP and energy scoring. 

[MarkyP]

I've done EWI to my bungalow renovation and a few things to consider. In my view the best insulation choice is graphite enhanced EPS. However, unless you have existing insulation in those walls, 50mm isn't anywhere near enough to meet regs which you should aim to better in any case. If your builder proposed Jablite then I think this will be EPS which is a start however the spec sheet doesnt say what type - you need to check they are using an EWI grade EPS sheet, this will be grey coloured (graphite enhanced) and more insulative than the white stuff. It should also be from aged blocks which are dimensionally stable, again EWI grade will be such. Even if you do have insulation in the walls, go for as much EPS as you can accommodate with your eaves/verge overhangs. The thicker the better. 50mm isnt very much at all and adding thickness isnt the main cost driver here, EPS is pretty cheap. I'd go for at least 120mm or more.

 

check out green building forum, search for "DIY EWI installation thread" to read all about my install. i did it myself and spent more time than I care to admit researching it!

 

things to watch out for -

 

- make sure the installer foams the joints in the boards. If they pug them with adheisve this is creating thermal bridges and is bad practice (but very common practice!)

- ensure they use branded, EWI grade EPS (I used kaycel) 

- ideally they should use thermally broken fixings and adhesive, the fixings are recessed and have a insulation cap, really neat (see my thread on GBF)

- avoid an aluminium tray at the DPC if you can, plastic is better and doesnt create a cold bridge.

- you dont need to break the insulation at the DPC contrary to building folklore it really wont matter or create issues but your installer might not agree. You could run run the insulaton right down to the top of the footing. Alternative is to break with a plastic plinth bead at DPC and run a course of EWI under the DPC level to the top of the footing. The aesthetic of the different DPC levels will be a fiddle but how you detail the below DPC insulation will be a factor.

- through colour render isnt my favourite, I prefer thin coat with mineral silicate finish. I used Baumit star contact white basecoat and nanopor fine finish.

- think about where you might need to mount rainwater downpipes. You cant fix into EWI, you can put timber grounds behind the insulation to screw into, or fix right through into the underlying wall

- frameseal beads for windows are really neat, check if they use these if not sugges tthey do, rendering up tthe window frames is scruffy and will need to be siliconed to create a weather seal

- EWI is a great solution - will make the house much warmer and the insulation is inherently wind tight once installed and rendered (unlike brickwork and cavity fill)

 

[MarkyP]

hmm, your window extension sills may not be big enough, this may be an issue. Mine were clip in and came in various sizes. Looking at the pictures (which may be deceiving), they look barely big enough for 50mm EWI, check that you can accomodate 50mm insulation plus 10mm adhesive plus 10mm (or more) render plus ideally 30mm projection for a drip. And ss above, 50mm really isnt enough insulation for regs unless you have existing, and in any case you really ought to do as much as poss while you are at it but the sills may be a constraint now.

 

also ideally take out the soffit and run the insulation up the face of the wall to the underside of the roof (be midnful of ventilation though), between rafters/joists such that it can meet the loft insulation. If not you get a cold spot at the top of the wall and window heads where there is no insulation. it will mean running new soffit or refitting cut back original sofft but again an important detail most installers wont bother with as too much trouble.

 

if the below DPC EWI seems too much to contemplate at the moment, the builder will run PVC starter track along DPC in all liklihood anyway so you could do the below DPC EWI later when you can face digging it out to the top of footings and installing. if the renderer is good get his number and see if he fancies a little side job to come back and do it later. If you end up with 50mm EWI then think about a drip or bellcast bead as you will not want less than 50mm below DPC and will need a drip detail of some kind to create a small overhang at the join.

[canalsiderenovation]

I need to check our info and confirm exactly which spec of insulation it is. I now know it needs to be the grey/graphite version of EPS. We do have cavity wall insulation on the existing as when they took the old windows out it was inside like white fluffy stuff and we found some paperwork when we bought the house confirming cavity wall insulation.

 

The window sills and eaves/overhand definitely won't be big enough for anything over 50mm unfortunately, we have checked. Very frustrating and an oversight really I should have picked up on.

 

Our soffits etc have gone in but I'll ask the builder when I see him tomorrow.

 

55 minutes ago, MarkyP said:

also ideally take out the soffit and run the insulation up the face of the wall to the underside of the roof (be midnful of ventilation though), between rafters/joists such that it can meet the loft insulation. If not you get a cold spot at the top of the wall and window heads where there is no insulation. it will mean running new soffit or refitting cut back original sofft but again an important detail most installers wont bother with as too much trouble.

 

Below DPC is happening the same time. I thought the below DPC should be else than the main EWI so 30mm?

 

57 minutes ago, MarkyP said:

if the below DPC EWI seems too much to contemplate at the moment, the builder will run PVC starter track along DPC in all liklihood anyway so you could do the below DPC EWI later when you can face digging it out to the top of footings and installing. if the renderer is good get his number and see if he fancies a little side job to come back and do it later. If you end up with 50mm EWI then think about a drip or bellcast bead as you will not want less than 50mm below DPC and will need a drip detail of some kind to create a small overhang at the join.

 

[MarkyP]

good to hear the below DPC is in the plan, this is a detail which seems to be more standard now, a few years' ago it wasnt.

 

the builder will likely use a starter track or plinth at the DPC line. This is based on the idea that the DPC needs to continue through the EWI (I'm doubtful it is needed, EPS doesnt wick water to any extent but your builder will likely want it). Lots of discussion on this point on green building forum. But if you do have a plinth/starter track you might find a bead that will create a slight lip and still allow 50mm below DPC as well. Or you could consider wehther you need to mark the DPC at all and run 50mm all the way down, but I appreciate this might seem bold and your builder might not like it and sounds like you havent got much time to research it. I did use a bead at DPC but only becuase I needed to get the EWI done and planned to do below DPC later when I had the time to dig out down to the top of the footings so the starter track gave me a level base to work from. I'm actually planning my below DPC EWI this summer, 4 years on.

 

if you need to backfill to bring the ground back to level (the plinth EWI should really good down to the footing) consider a strip of leca (clay pellets) - it's quite an insulative material and will create a further benefit in addition to the below DPC EWI and will help keep the area around the plinth EWI well drained and dry. Again check out GBF and search for "EWI & leca" there's an architect who posts with some really good ideas and experience with EWI.

 

hope the admins dont mind the GBF plugs, EWI has been discussed there in great technical depth so is really worth a read.