Hi all

I'm a newbie here and my technical knowledge/understanding is limited but is improving all the time as I have spent quite a while searching this forum.

We are building a timber-frame closed panel house this year, which is 190m2 over 3 floors (using attic space). I know we are probably falling at the first hurdle in terms of being green due to the size of the house but it is very well insulated and airtight (with MVHR) and so should be very energy efficient.

Which brings me to my question...how do we decide on the best way to provide the heating requirements? We plan to have ufh on ground floor with rads upstairs and towel rails in bathrooms. We also would like a small (5kw) room-sealed wood burner in the living room for occasional use. I know this is a 'want' rather than a 'need' but this is non-negotiable as far as my husband is concerned.

The architect has specified a condensing boiler with megaflow cylinder. Ideally I would also like to install solar thermal and link this in. I have read lots of threads on here re. thermal stores and admittedly have got rather confused about whether we should use one or not. The budget is tight so cost is obviously an important factor. This may seem a silly question but who exactly am I meant to be asking these questions to? I want unbiased, independent advice on what our heating needs will be and the best way to supply them. I'd be grateful if anyone could point me in the right direction!

Thanks

The question has to be what do the figures say. If you are investing enough in the insulation, getting enough solar gain, living in the right part of the country, then a traditional heating *system* may well be redundant.

My plan is to have UFH in some parts, and small electric panel radiators elsewhere. I will be using Solar Thermal to heat a large tank; DHW using an on demand system. The intention is not to heat a tank by gas that 'may' be needed, rather heat it when I know it is and the ST cannot provide.

All sorts of factors affect this decision and none of the assessments will tell you 100% what will happen as houses have a habit of performing differently to predictions. If it is airtight and well insulated (well above the current requirements) then you may not need a traditional heating system but you need to do some proper assessment.

Matkat01

You didn't say whether the condensing boiler is gas, oil or LPG. Can you confirm which? It makes a difference to the economics.

If the house is getting close to Passivhaus standards then water heating becomes the dominant load. Solar thermal I would definitely recommend. If this is not affordable at present get a twin coil cylinder of 200 litres or more so solar can be added in the future. Ensure the heat loss from the cylinder is <1.6 kWh per day (a genuine Megaflo will meet this).

If you are in a mains gas area then on balance gas is as good an option as any. ASHP or GSHP will have lower running costs but I have found the paybacks on well insulated new builds vs gas to be uneconomic.

If you have copies of the SAP calculations to hand the full DER report should indicate a 'Space Heating Demand' and a 'Water Heating Demand' which can be used to work out the paybacks. Forward these if you have them and I will show you the methodology.

If you insulate really well you wont need a heating system, its installation, running maintainence or replacement costs.

I did use 300W of additional direct electric heating for two weeks this winter but have a new house with no heating system.

I do try to save some heat from summer to winter if I can.

Insulation is very cheap to build in but very expensive and sometimes almost impossible to retrofit.

Thanks all for your comments. To answer some of your questions:

GaryB: The condensing boiler is gas. We are about to get the SAP calculation done in the next couple of weeks, so maybe I should be waiting for that to be done first!

Ed: No, we are not planning to have a boiler linked up to the stove as it is really just a small stove for occasional use.

tony: I wish I was brave enough to not put a heating system in, but even if the figures indicated it was do-able, I'm far too cautious to go down that road...it would certainly help the budget figures though..

Timber: I'm not sure if I used the right term, but it is a Timber Frame with all the external walls, including windows and doors, being factory fitted which obviously helps with airtightness The panels are then craned onto the foundations, along with the roof structure and then builder takes over. The walls and roof have a u value of 0.14, and we are using an Insulslab foundation system with u value of 0.11 - 0.13.

Ah ok, so propper closed panel. I would just double check about detailing of windows etc to ensure that the detailing is up to scratch.

Who's system are you using? Whisper it to me if you don't want to openly name them.

With closed panel systems, you do need to ensure that the building goes up quickly and protect the panels from the weather if it going to take more than a few days to get the building weather tight.

Well what I mean is that don't assume that the detailing is great without looking at it yourself. I am not saying that the detailing at junctions isn't up to scratch, but please check it for yourselfs.

The TF manufacturer should have a set of standard details for their juntions and window installs. Ask for them and check they out.

I can't offer any advice over and above what others can offer (not my bag) but hopefully the heating system will be minimal with claimed U-Values that low and hopefully good air tightness.

Posted By: matkat01I must admit I was a little concerned about Munster initially as there are some dire reviews about them on the internet, but I understand they have moved on a lot in recent years. At least, I hope so!

Heard only good things about them recently.

When I looked at Munster windows a few months ago I think they were up on a par with Internorm, with Ug (centre) of around 0.5 and a Uw of around 0.7 I believe. This was their Passivhaus certified one, can't remember what it was called. They are a fair bit cheaper than Internorm, which is why I was looking at them.

Munster are 0.65 for their PVC window,

Viking, do you know what window range that is please?