Hi all,

Having joined the forum a couple of years ago while waiting for the purchase of our house to go through, I have definitely learnt alot and we are now ready to crack on with things.

I do tend to be a bit of a perfectionist, however, as much as I would love a passive house, I realise that given a 130 year old building and a fairly limited budget, there is going to be a fair bit of compromise.

The ideal solution would have probably been EWI all round with some sort of reclaimed brick slip finish - far too costly obviously, we didn't really want to loose the brick and are in a conservation area so would probably have had little choice with the front at least. As such, we've decided to split the work into two main phases - with one part of the building being primarily IWI, which will be happening first, allowing us to redecorate most of the house at the same time and the other EWI, coming at a later stage, when funds allow.

The 'phase 1' plan is:
Walls (blue on plan) - 80mm Woodfibre w/ lime render IWI giving 0.39ish u-value (possibly eps instead in ensuite)
Suspended floor (green)- 200mm mineral wool breather membrane 'hammock' for support and VCL over the top, existing pitch pine boards to finish giving approx 0.19 u-value
Attic rooms - 40mm celotex between rafters (leaving 50mm ventilation gap, felt lap vents to be fitted), 100mm celotex over top, boards taped with aluminium tape and an airtight tape to the walls, possibly battens to form 25mm service void then 12.5mm plasterboard giving a u-value of 0.16
Windows - these are currently badly fitted UPVC casement windows, looking to change these to new UPVC sliding sash's - appreciate that this could be a little controversial but given the budget we have, these seemed a good compromise between making some improvement and the overall cost.

Phase 2 would be converting the remaining 'back' roofs to warm roofs, whilst extending overhang for 150mm EPS EWI (red on plan), down to footing. New windows/doors fitted outbound in insulation layer.

A few questions:
- BCO suggested 100mm celotex be reduced to 75mm due to risk of interstitial condensation - he wasn't too bothered either way but given a decent VCL I'd have thought 100mm would pose no additional risk?

- Woodfibre boards - any recommendations for a 'system'? Looking at ecomerchant's steico/breathaplasta as it seems fairly simple compared to some others and competitively priced.

- How to people handle heavy fixings in woodfibre e.g. curtain poles, radiators where these can't be moved to an internal wall.

- Internal Partition wall returns - I was looking at doing these in something like 30mm boards, coming in 500mm or so and tapering to avoid any steps. Not too sure how I'd achieve this other than a fair bit of time with a rasp?

- Trickle vents - BCO wants these fitted, I'm not too keen on the idea of spending time taping and parging to improve the air tightness, just to spend a load of money on new windows with a big hole in, undoing all my hard work. I guess the only other option is MVHR though - is this ever going to be worth fitting given that even with my best efforts this is still likely to be a fairly leaky building - I have half a plan involving ductwork down chimney's but given the extra costs and possibly limited usefulness, perhaps trickle vents are the easier options

Sorry for the long first post and thanks in advance, would welcome any other comments/thoughts on the above too!

Its difficult to see from the picture - is it solid wall everywhere or is there cavity in places?

For windows I'm with djh, why sash windows? I would go for good upvc casement tilt and turn windows.
And they look tall enough to have tilt and turn on the lower half with fixed lights above but make sure the frames top and bottom are the same width because fixed lights can be standard frames without opening light s inset which gives a wider glass area but lould look silly.

Bay windows can be particularly nasty in terms of cold ingress. These deserve particular attention especially the flat roof part both insulation and its water tightness. What plans?

Radiators - You can get legs for radiators which transfer the weight to the floor. If you use these and then fix the usual brackets screwed through the IWI this should be OK.

A few scatter-gun comments.

Is the drive to the R of the RHS rendered wall yours? If not can you negotiate to buy a bit of your neighbour's land? A client of mine did this.

Assuming the 50mm ventilation gap really is ventilated (I often see lovely gaps and very poor 'ins' and 'outs') then 75, 100, 150 (looooong screws!) is going to make little difference. The beauty of properly-ventilated roofs is that the WV does not get to hang around long enough before being blown away.

Wood-fibre. I have used Pavatex for years, with Baumit plasters. The latter very 'friendly' to use.

Re rasp, don't get out your surform, as I used to. Buy an EWI rasp, which is like a cross between a cheese grater and a large plastering trowel. Made for EPS AFAIK but does the business on WF.

Agree avoid sliding sash if really going for A/T.

If you are not going for HRV then you need to prove to BCO that you have 'enough holes' somewhere. If you go for HRV in the long term trickle vents can be removed and blocked.

@db8000, I am just racing the weather doing what you propose. In fact we finished the render yesterday on about 120-ish m2 of Victorian cavity brick wall with (on one elev) 120mm and (on the other) 160mm wood-fibre. Went to and fro between WF and (much cheaper and lighter) EPS, particularly in the light of a bad back and boards weighing about 23kg, but heart said WF. Ours is detached, and 2 elevs built to 'show off'. It's not that pretty, but all the fancy detailing (stone plinths, keystones, rubbed brick arches, ornamental brickwork round windows, bay windows, faces the road. The other 2 walls are 'ar$e-end-of-a-terrace' architecture - fine enough to no letters home.

Yes, return the IWI to cloak the thermal bridge - in full depth if you can. I find the Nick Parsons dual-depth purpose-made bookcase concept works here.

Posted By: ballenChimneys - All of ours are external and in need of repointing above the roof line. I was considering blocking these up and filling with something like vermiculite - possibly using the space to run MVHR ducting to the ground floor living room and dining room. I've seen alot mentioned on doing this with internal chimneys but get the impression external chimneys could be riskier. Any thoughts on this?

Usually, MVHR ducts are run in the internal (warm) spaces, because they're carrying air at near room temperature. If they're installed somewhere outside the thermal envelope, then they need insulating quite well to avoid defeating the purpose of an MVHR. Internal chimneys are automatically insulated as long as they're closed at the top, but external chimneys would obviously need to be insulated. Depending on your plans this might be something you do anyway.

PS The (short) duct runs to the fresh air from the MVHR unit need to be insulated because they are carrying air at outside temperature. Hence mounting the MVHR somewhere near an outside wall is usually a good idea.

Ballen said: ''What are you using on the woodfibre boards RK70?''

Sorry for late reply. Yes, I use RK70 and the 'Kalkin glatt' final finish, which is OK to use but very different to 'pink plaster'.

Remember if you have existing lime plaster and it is not all clogged up with gloss or vinyl silk you can use that as the parge coat and simply augment where required. I always 'butter' the boards with a 10mm toothed-trowel coat of RK70 so that if my parge coat is not perfect the 'buttering' will fill any hollows.

My house has sand/cement re-pointing and some spalling brickwork, but it had spalling before we did any IWI. The 'rate of attrition' seems no worse.

I am working on retrofitting 3 separate "small" mhrv units to our 19thC stone house, each extracting from one room and feeding into an adjacent room*. Reasons:

- easier and much cheaper than trying to run ducts to a big manifold in a central location with no existing routes
- compatible with slow bit-at-a-time renovation
- several small mhrvs much cheaper than a single house-sized one
- allows ventilation at the right time - eg boost the kitchen one when cooking, and the guest bedroom one when there are guests, instead of having to boost the whole house
- allows different temperatures at different times in different rooms without losing efficiency.

* Though one of them is a through-the-wall

We are looking at hr100r "two room" units which are basic but fit for our purpose. However they seem to be getting towards the end of their products life, and the replacement model is much better and hence too expensive.

Many 19thC houses didn't originally have indoor bathrooms/ wet rooms etc, so it is common to find an early-20th-C extension out the back with a kitchen and utility or shower room downstairs and a bedroom and bathroom upstairs - IE with all the 'wet' rooms grouped around a single drain downpipe. Our last 4 houses were like that, as it seems is Ballen's.

This makes it relatively easy to have all the intakes/exhausts on the same wall.

For example on Ballen's floorplan:

Mhrv unit #1 could extract directly from the kitchen, and supply into the dining room through a short duct with no manifolds. Unit located in a kitchen cabinet, intake/exhaust straight thru the kitchen external wall.

Mhrv unit #2 could extract directly from the laundry room and supply through the wall into the breakfast room. Located in the laundry room, in a cabinet on the partition wall between those two rooms.

Mhrv unit #3 could extract from the upstairs bathroom and supply into the adjacent bedroom. Located above the bathroom ceiling.

And so on.... Ballen has five wet rooms (we have fewer) so they might want up to 5 mini mhrvs, depending how many bathrooms are in use often enough. 5 off HR100R @ £270 each, no manifolds, minimal ducts = £1600. Costs more to have better units.

Whilst I'm a big fan of semi-rigid ducting (it's what we have for all the internal ducting), I'd recommend choosing a product that has a smooth internal surface rather than exposing ribs internally. The difference is quite significant, I believe. I second the opinion about minimising bends and especially corners.

I can see that if all the wetrooms are in a vertical stack obliged by a single soil pipe, then in that case single room MVHR units could work. But I don't think Ballen's place is like that. It has three wetrooms spread along the length and height of one wall, but then two more in the opposite corner. So I'm still left with the puzzle I mentioned.

I like Blumartin's product, but I'm less convinced by the push-pull systems - maybe I'm just too sceptical. The push-pull units are quite low capacity, so you'd need quite a lot of them.

Posted By: WillInAberdeenFor example on Ballen's floorplan:

Mhrv unit #1 could extract directly from the kitchen, and supply into the dining room through a short duct with no manifolds. Unit located in a kitchen cabinet, intake/exhaust straight thru the kitchen external wall.

Mhrv unit #2 could extract directly from the laundry room and supply through the wall into the breakfast room. Located in the laundry room, in a cabinet on the partition wall between those two rooms.

Mhrv unit #3 could extract from the upstairs bathroom and supply into the adjacent bedroom. Located above the bathroom ceiling.

And so on.... Ballen has five wet rooms (we have fewer) so they might want up to 5 mini mhrvs, depending how many bathrooms are in use often enough. 5 off HR100R @ £270 each, no manifolds, minimal ducts = £1600. Costs more to have better units.

Yes, I see. So you are kind of taking advantage of the partition wall between adjacent rooms as a way of putting some distance between extract and intake points.

Posted By: WillInAberdeenI can't speak for the layout of Ballen's house, but it does look like all their wetrooms are adjacent to the cream painted wall in the picture.

Eh? The plan shows a laundry & WC, a kitchen, and a bathroom against that wall, and an ensuite and another WC against the front wall at the right-hand side.

I'm curious what you or they mean by 'self-balancing and by how it works. The term doesn't appear in the Lunos catalogue so do you have a link to a description please?

My dislike of the push-pull units is just personal prejudice. I feel an instinctive distrust of systems that rely on passing exhaust air and fresh air over the same surfaces and rely on those surfaces staying sterile for many years. I know the manufacturers say it is all fine.

Yes, I understand the two-room units and also the Blumartin 'ducted exhaust but not supply' arrangement.

One other issue to be aware of with two-room or other short ducted units is that it restricts the placement of the terminal in each room quite a lot. So it's worth checking that the resulting placements are sensible. Obviously the flow rates need to be compatible as well.

The bathroom and the downstairs WC are definitely against the opposite wall. The kitchen I agree spans the two

Unfortunately EN 13141-8 is one of those standards where you have to pay money to read it. So I haven't. But https://www.partel.co.uk/product/lunos-e60/ , which refers to the standard, says "An optional, intelligent control system ensures that the occurring back pressures are balanced up to 20 Pa" so apparently (a) it is optional and (b) the requirement is only up to the low end of a Beaufort Force 4 and considerably below the 50 Pa used for airtightness testing (and higher values are used in particularly windy countries, I believe). So it doesn't really answer my question I think.

The single room units I'd been looking at were the push-pull, but it did seem like I would basically need a unit for each room - becomes quite expensive and their not that aesthetically pleasing. Likewise for something like Fresh-R which looked like it would require multiple units and again, soon add up in cost.

I quite like the idea of multiple small units working between two rooms - not something I'd come across before and has certainly given me something to think about. I think what you've suggested would give me something like the attached - with red being extract and blue supply.

The bedroom/en-suite unit would likely live in the cupboard next to the top floor WC - I'm thinking these could be combined although I might need a bigger unit? Perhaps I could then feed supply's to the remaining two bedrooms?

This would then just leave the lounge without any sort of ventilation - is this acceptable or would I need an alternative e.g. push pull unit here?

The biggest issue with this proposal is the dining room/kitchen arrangement given the slightly awkward ducting in the kitchen and across the hallway. This could probably be boxed in quite satisfactorily although I believe it still leaves the supply vent in a less than ideal position.

I'm somewhat torn between this idea and a whole house unit - for which I think I have duct routes worked out for everything but the living room again. However, would be more difficult to install and require a fairly big (expensive) unit I believe.