Hello to everyone!

Like many others I have been regularly visiting here as a guest user in search of inspiration, information and explanation, but as my build plans gain momentum the time has come to join the community and get involved.

My wife and I are hoping to build a 1.5 storey home of around 335sqm with a traditional vernacular farmhouse appearance and an ambition of finding the sweet spot between capital outlay and low energy bills/ good comfort levels.

We're at the Building Control stage at the moment so my arrival here is in many ways to sound out ideas in a bid to make them work cohesively as a cost effective package. While I admire and draw inspiration from the Passive House principles, PHPP was not our starting point and as time has gone on I am realising the rules of diminishing returns can be applied to many decisions the would be self builder faces. This has been a tough pill to swallow in some ways as both my wife and myself are only children who like our things to be perfect!

We've had the pleasure of meeting Seamus from Viking House and as well as pricing us a timber package he showed us a recently built home primarily heated by a large solar collector.

Well that seems like plenty of rambling for now, time to explore the full realms of the forum as a paid member!

The Planning Service produce a Design Guide for Rural NI that explains in quite some detail what is desirable, but a brief summary of our design would be a linear 3 room cottage with adjoining stone outbuilding (which is our kitchen) and hopefully the impression that the house has evolved over time with two rear extensions, making it more of a T shape. With quite a high wall plate level, a limited palette and simple lines (no projections at eaves etc.) overall it has a fairly austere appearance.

Although far from ideal in terms of the area of external walls, our design is basically one room deep throughout. I personally feel this results in more pleasing proportions and combined with the high solid to void ratio, circa 38 degree roof pitch and vertical emphasis to external openings on paper at least satisfies most of the recommendations in the Guide.

We managed to push the envelope of our Outline Planning Permission slightly which stated the house should be "of single storey construction" but had no ridge height restriction. We ended up at around 6.5m ridge height, no dormers, just roof lights and gable windows and seemingly in Planning terms this is still seen as single storey.

Rear, we made some amendments since this was done though:

A flat roof?!!

Good morning and thank you for the comments!

The flat roof area has a fall of around 3 degrees and will have a standing seam zinc finish, hopefully resulting in something similar to the attached photograph. This area originally contained the pantry and boot room but after some tweaks we moved the boot room closer to the outbuildings and made space for a formal dining area outside the kitchen which opens to a paved area at the rear through French doors.

The first floor has an internal span of 5.3m and height at the eaves is just over 1.3m. This assumes 100mm PIR over 150mm rafter filled with spray foam insulation and a 50mm service cavity. The flat roof has a similar construction except for the covering. The energy consultant I spoke to says this build up gives an airtight warm roof that is "easy to do right" and claims a U value of 0.12. The SAP report suggests the average to be more like 0.14, but this may(?!) be due to a different (brand) spray foam being used in his calculations.

I have some reservations about this approach and one alternative I'm looking into is the possibility of using a glulam ridge beam with timber I joists sheeted top and bottom with something like OSB and pumped with silver/ platinum beads. I have received one quote for the beams and joists so far but don't have enough information to know whether this would be cost effective or even work as a system. It would probably sacrifice about 50mm headroom if we keep the service cavity but I believe the U value would be closer to 0.1.

The front of the house faces SW and it is the house only that is 335sqm. The outbuildings deliberately face directly South so that we could fit PV at a later date if we choose, but heating is likely to be from a heat pump. Due to the rocky nature of the site a GSHP may require bore holes making ASHP more economically viable.

The house Seamus showed us had a similar orientation and while without question I found the solar heating impressive, the potential grants etc we could qualify for in the North would probably make the heat pumps more attractive financially.

The SAP report is quite a jumble of numbers to me too and the present version seems to include some provisional figures so while there are pieces of information that may be useful, not all of it can be accurate. The various measurements do seem quite comprehensive though and suggest they account for orientation, overshading and thermal bridging.

It suggests the annual energy cost would be £1899 which at about 17p/unit equates to roughly 11170 units. If I understand the calculation, dividing 11170 by the area of the house means the energy requirement is approx 33.35kWhr/m2/a.

I believe this figure includes hot water and lighting (both of these are mentioned in the report at some stage) and think some of the provisional values will be rather unkind to the predicted results (such as Air Permeability at 50 pascals as 10.00). Apparently the fact we are including MHRV is quite detrimental to the "score" as it uses electric and we would currently be rated as C73 for Energy Efficiency Rating and C76 for Environmental Impact Rating. Given the lengths I think we are going to this is rather disappointing, but I have been assured the "As Built" report will make better reading and that the assessment isn't very accurate for low energy type homes.

Another item that will no doubt affect the score is our potential window choice, a topic that my wife and I seem to deliberate endlessly and usually results in me searching the internet for hours in search of the mythical beast... an efficient, airtight sliding sash!

As previously mentioned, our design is rather plain and we feel it will fall upon using the correct finishes such as the roof slates, render finish, the stonework, the rainwater goods and definitely the windows to show the traditional character we are trying to achieve. To both our minds the only acceptable aesthetic for the windows is the sliding sash, not only due to the style of the house but also the shape of the openings.

There are offerings out there with A ratings but these are usually PVCu and when I mention to suppliers they are for a low energy house they usually suck air through their teeth and say "you don't want to do that, they'll be rattling and drafty in no time". This hardly inspires confidence when it comes from the people trying to make a sale!

Another common thing I seem to hear from window suppliers is that triple glazing (in sash windows at least) isn't worth the expense and that gasses like krypton will have leaked after 10 years reducing the performance to below that of double glazing. Add to the confusion that they say some windows can be A rated when double glazed but drop to a B when triple glazed as solar gain and the level of light that pass through are also measured and the whole thing has my head in a spin!

In truth, with having MHRV it is perhaps going to be a rare occasion that the windows will be open so the actual way they open isn't of the utmost importance. I have started looking into mock sash windows and while there are options available that tick the appearance box, many seem to only accept a 24mm glazing unit and are fairly basic in their draft proofing.

Alternatively, there are products that seem to perform exactly how we want in terms of insulation and air tightness but invariably fall short in the looks department. The two characteristics that seem hard (should read so far impossible!) to find in an efficient window are getting the sight lines in the glazing to match up vertically between top and bottom pane and that the top pane should sit proud from the bottom by an amount that gives the correct impression of depth. Many mock sash windows have a wider glazed area in the lower pane and a rather flat appearance, especially if they are advertised as storm proof.

If you managed to follow all that and haven't fallen asleep I'd really love to hear any suggestions anyone may have for potential window suppliers. I appreciate care should be exercised when recommending or shaming businesses on the forum so please feel free to whisper if that is preferable:)

Slider

Welcome to the Forum from another Norn Iron member!

Your house definitely has a rural NI vernacular character. Are you in the Mourne conservation area, by any chance? The house looks very similar to a number of vernacular restorations we were involved a few years back for the Mourne Heritage Trust.

BTW, you need to get a new SAP assessor. There is a complete disconnect between the description of the house and its servicing and the SAP output figures. It looks like default SAP values have been used all over the place.

Slider

Agreed that at this stage the actual SAP value is not critically important as it meets the Building Regs, except that you may be making decisions on the basis of inaccurate life cycle costs.

You will need to have an accurate EPC however as it may affect the resale value of the house and the amount of future rates payable.

Mine and an0ew, recently completed in Bristol

Slidersx200,

How have you got on? My view would be triple glazing is a must. If companies are telling you go double it's because they don't do triple! A lot of companies are also doing deals for free upgrade to triple. Our new build has large quantities of glazing south and west and the passive solar is great, with minimal heat lost. We original wanted a aluclad timber but the budget only stretched to aluclad pvc.

Regarding energy efficiently ensure you have as airtight as you can and go with heat recovery, it's a great job. We have underfloor heating through fed from a 1000Ltr accumulator tank, heated by solar and wood burning stove, it works but I'm trying to iron out some issues to make it more efficient.

Best of luck with the build.

Love to hear what company are doing the sash windows so I can have a look. Might know of a company here in Northern Ireland that can do it, I've seen first hand the fantastic job they did of restoring old sash windows but unsure if they will make new ones.

I actually looked up the website of the company I came across and I must say I`m even more impressed. Their a local firm if you want their details I can give them to you?

Slidersx200

If you have any queries let me know I'm just down the road, I'm just finishing a self build. My window are very modern but I'll check my supplier to see if they do anything more traditional
O see if they do something

Regards
archmoco

Check out Dask timber.They have a very good website saw their conservation work repairing sash windows on a job I did and was impressed. Some nice details on their website.

Cheers mackers,

Must be a good product, I think every house in their photos is a Des Ewing design, which also may imply they're rather pricy! Might give them a ring anyway.

Heron Joinery have a very comprehensive range, but the guy I spoke to on the phone was another false promiser who failed to get back to me, so that went in the bin!