TFnovice

The planning has already been granted. We pushed the height to get 1.5 storeys so are already at the limit. I'm a bit concerned about future flood risk (down the 'hill' but not far) and feel it would be foolish to be thinking in 10 years time under 100mm of water that I could have avoided it if only I hadn't lowered the floor level. I'm aware of the thickness of a line argument and we might well get away with it, but if you purposefully design in your 100mm tolerance then you no longer have a build tolerance! Can someone confirm whether it is preferable to put the 100mm (or whatever depth) above the rafters or below? TIA

OK, so would you put the 25mm over or under the rafters? Sorry for the dumb question. One of the reasons for having a 1.5 storey house is the height restriction, so increasing the height of the roof by 100mm might be restrictive. Alternatively reducing the internal height could cause issues in some areas eg showers in bathrooms where head height in certain places is particularly material.

Thanks all - very interesting and useful. I'm planning on using 160mm of Kingspan Kooltherm K107 insulation between the rafters under Spanish slates. I think the proposed insulation will offer a U value of about 0.15. No idea of the decrement delay or even how to find this out!

I'm wondering whether anyone has real life experience of this... We are building a 1.5 storey house with rooms in the roof. These can be prone to overheating in summer and so I am planning to mitigate this as much as possible by keeping temperatures down during the day. I'm considering an in roof PV system on a small south facing roof which has bedrooms below. I've been quoted for a 2.7kwp Clearline system (12 panels). These are pretty low profile which is one of my criteria but I have read that the panels reach pretty high temperatures and need to be vented to perform properly (which seems to be at odds with designing them to be low profile). I am wondering whether there is a risk they will transfer some of their heat to the rooms below? Does anyone have a similar installation who could comment or other real world experience?

This is a great project - quirky with opportunities for split level living which can work really well - very jealous! I'm with Ferdinand on the fact that you need to be looking at the layout first. What you've proposed is still a compromise and your budget would allow you to improve it hugely - the layout should dictate the entrance. I think a split level house can be a real asset if it flows well inside. That all depends on how you live as a family - decide what spaces do you need for living and sleeping then consider changing the use of some of the rooms - eg study/bathroom to become a guest bedroom suite as said above. I would also say that the best split level houses tend not to have standard narrow stairs between levels but rather wider more open steps which stop it from feeling like you are constantly on the wrong level. You want to keep the bedrooms separate but have the living areas flowing.

In what way is your site exposed that put them off - wind? cold? Not sun I presume. Sorry to hear about the issues you are having with Internorm. Doesn't sound very encouraging. Where are they leaking? Have the windows themselves failed or is it an installation issue?

Interesting - one of their agents/installers told me they were being withdrawn as they were a huge maintenance nightmare. Maybe it was just that agent who was fed up of calls outs to fix.

Wow. Sounds like I have some work to do!

Sounds interesting - could you post a photo and details of the manufacturer? Also interesting - which coating type did you go for?

I was talking about continental style shutters which are either open or closed. They do have a mid setting which lets a tiny amount of light through but not really enough. I have seen the internal Venetian blinds but I don't think Internorm are offering those any more. They said they had a lot of problems with them. We also have quite tall windows so when the blinds are retracted they would occupy a large amount of space at the top of the window. External Venetian blinds which retract into the reveal would be interesting.

Nice once you've got your planning in place though!

This was one of my first thoughts and I have looked at Internorm who offer the same. But I'm just not sure dark rooms are what I want in summer. Not come across Gaulhofer before. They look interesting - how do they compare price-wise? And do they cover the whole of the UK. I see their agent is in Fife. I'm surprised that is a planning issue - guessing you must be in a conservation area or AONB.

Thanks, this is interesting and we are in the same position. The large overhangs would also not work with the design of our house. I have looked at louvres, but this creates a problem with cleaning the windows. I have contemplated continental style external shutters but these leave rooms we would want to use very dark. At the moment I've settled on heat insulating internal blinds. Whilst these don't stop the heat getting through the glass they do at least stop it heating everything in the room. So hopefully the solar gain will be minimised. When you say 'modelling' was this done by you or did you get someone else to do this for you? I presume it was more than just a SAP calc. A cooling element to the MVHR system would only really be to stop it from pulling in warmer air from the outside than the air temp inside and effectively heating the house. I suppose I could always just turn it off on hot days, but I wasn't sure how happy it would be with being turned on and off regularly and whether this would put it out of balance. To be honest I haven't looked at the extra over cost of one which cools over a standard one (eg the Zehnder or Genflex). I only know that the 'all singing and dancing' quote I had from THE was a little eye watering and I'd had some surprisingly large quotes for MVHR already. I will have a look at the A2A systems available (I'm getting the hang of the abbreviations) and see whether they are cost effective (ie cheap enough) to warrant installing for the relatively limited use they will get.

I would guess 2 - 4 weeks, so not a nightmare but worth consideration at the design stage.

Thanks for the explanation, but that all sounds much too complicated. I think I'll look at the air-to-air suggestion and stick with gas UFH and MVHR. Yes but on the days when it's hotter outside than in and there is no breeze, all that does is exacerbate the situation.

Yes thanks. The position of the house is fixed as is the design. 350 days of the year there should be any issues. Just trying to mitigate the other couple of weeks and the risk of changes in weather patterns affecting us in the future!

Thanks - I'll do that. And can I use a gas boiler for heat and an ASHP for cooling on the same UFH system do you know?

Thanks - I'll have a look at those in a bit more detail. I saw you had mentioned this elsewhere and your set up sounds very well thought through and effective. Total Home claims their own design system is significantly better at cooling than the Genvex or the Zehnder. Is there any way to measure that without actually seeing it in operation (I'm no engineer as you may have guessed)? My thinking was more that when the ext temp is higher than the int temp of the house, even with a summer bypass you would be drawing in warmer air which seems crazy. The cooling is really just to keep the air flow but stop that from happening. This sounds an interesting option - can anyone answer this question please? And maybe point me in the direction if how it works?

Thanks for the reply. When you say air-to-air heat pumps are you talking about this sort of thing? https://www.daikin.co.uk/en_gb/product-group/air-to-air-heat-pumps.html I was hoping that there would be some sort of combined system that would do it all. I would like to avoid boxes on the wall for cooling as they aren't very attractive. I have found this combined heating/cooling MVHR system which the manufacturer claims is significantly better than, for example, the Zehnder ComfoCool. Does anyone have any experience of this system? http://www.totalhome.co.uk/images/HPVSummaryPage18.pdf If I wanted to go down the route of cooling the UFH in the slab, can that only be done with ASHP?

Awesome. Sounds very exciting. You are slightly ahead of me. Will watch with interest. And good luck!

Sounds like a plan. Will do. Note from your profile you are looking for a site - still the case or have you found something?

Thanks @Dreadnaught. I think the learning curve will be steep and I'm expecting to make a few mistakes along the way (although that won't make them any less frustrating). A great idea to visit other builds. How does one go about finding those?

New here, liking the forum very much and particularly interested in this thread! We are building a timber framed house (not passive) and I am trying to get a handle on the heating and, hopefully, cooling. The range of options and new tech is bewildering. For the heating we are on mains gas so I ruled out GSHP early on (for better or worse) and assumed a gas boiler with in screed UFH on both floors. Pretty straight forward, but ideally I would like some (non AC) cooling too as we will get a lot of solar gain. Some of this will be mitigated with shutters, blinds or window film, but not all. Having initially been told you can't cool MVHR I have now come across two options, one which uses a GSHP bore hole and the other which sounds very similar to the system JSHarris has described above. Both aim to offer whole house heating and cooling. Neither are cheap and nor are they supplied by large well known companies and so I am a little wary. The comment above about cooling the floor slab is also new to me and sounds very interesting. Can anyone provide a link to a not too technical explanation and possibly the kit involved to achieve this?

Thanks. Once the planning is granted and I know things are finalised I'll do that.

Thanks Christine.