Certified passive house consultant Patrick McMullan of Co Tyrone shares how he went about designing and building his family home.
In this article we cover:
- Full costings, spec and floorplans
- Initial design and getting the space right
- Passive house effect on the design
- Cost savers
- Kitchen and bathroom designs
- Designing the outside space
- Passive house explainers
- Choosing external finishes
- Choosing windows and doors
- Securing planning permission
- Heating system choice
- Ventilation system choice
- Provisions for on site electricity, water
- Construction drawings
- Timeline and progress photos
Contents
Part 1 – Design stage – Skip to Part 1
Floor plans, specification & suppliers – Skip here
Part 1 – Design stage
The site we are building on is located in the countryside, on the family farm in Co Tyrone, which falls under the jurisdiction of Mid-Ulster District Council. It was always my intention to move back home and build close to my family, but what really motivated my wife and I to take the plunge was the need for more space.
House size: 250 sqm
Bedrooms: 4
Plot size: 2 acres
Site cost: gifted
Build cost: £250k
Construction: masonry cavity wall
Ventilation: centralised mechanical with heat recovery
Heating system: air to water
We had our third child last April and are fast outgrowing our current three bed semi detached house in a local town. Although prices across the board have risen quite considerably in the past number of years, we wanted the kids to grow up in the countryside, so we felt it was the right time to build.
We were extremely lucky to have been gifted the site which was a huge help. To be honest if we had to buy the site before we started the build we quite literally couldn’t have afforded to do it, so we realise we are in a very privileged position.
Getting the space right
The starting point for the style of house was a range of different ideas. Thankfully we have lived in a house with the kids for a few years which gave a great insight into things we would like which we don’t currently have or where more room would be a huge help. Had we built this house five years
ago before the children were born, I dread to think what monstrosity we would have come up with. It would have been a random mix of modern ideas from social media which just wouldn’t have been
practical and would have been expensive to build and maintain.
The aesthetic appearance of the house was very important to us, but the main criteria was that it be a
functional, low energy home that would be cheap to run and make the most of the space we had.
Upstairs we wanted four good sized bedrooms so the children could eventually have a room each and in the main bedroom we incorporated a walk-in dressing room and ensuite.
At this design phase we spent 90 per cent of our time planning the layout downstairs as there were so
many possible variations for everything. We only spent around 10 per cent of the time on the upstairs design as it more or less took care of itself. We tried where possible to keep the bedroom glazing on the west side of the build to avoid the morning sunrise.
Passive house effect on the design
I am a certified passive house consultant so was keen to keep the form factor as low as possible. So, the simpler the shape the easier it would be to hit the required metrics in terms of airtightness and U-values (see explainers).
Thankfully this played nicely into the style of house we wanted, as we both like the two storey modern/ Georgian farmhouse style. This style of house allowed us to make the most use of space as we had no irregular shapes to design around.
We wanted a nice open plan kitchen and living area as we tend to spend most of our time in these rooms. This meant orientating the kitchen to the south side of the build and incorporating slightly more glazing to take advantage of views and solar gains. We also really liked the idea of a larder to reduce clutter and keep the main kitchen area simple.
We decided to use the space under the stairs for a walk-in larder as it was likely to finish up just being a wasted space otherwise.
We also went with no back hall to make the utility room larger and used the extra space to incorporate a drying room within the utility. We stacked the wet rooms (toilets/showers, etc.) and kept them all to the north/ east of the build. This helps with the waste pipe returns and with the mechanical ventilation with heat recovery (MVHR) system efficiency as all the extract rooms are on one side of the house and the supply rooms on the other.
It also meant less protrusions through the exterior walls which helps keep the building airtight. This design means that there is no protrusion on the front or either gable wall which we felt was very important for the aesthetics. In total there are only two pipe protrusions on the entire house as the majority of the smaller waste pipes were joined inside the house within the suspended ceilings. We also went with a multipurprose room downstairs which for now will be a toy room for the kids but may be converted to a bedroom sometime in the future if required.
Cost savers
Budgeting on a self-build can be difficult because it’s a moving target – things change throughout the build. The biggest cost saving we have made, and it is massively underestimated, is by keeping the shape of the house simple. We essentially have a rectangular box with a straight truss roof and no chimneys. We have saved thousands on materials and labour in this regard and have got a more spacious, energy efficient home.
A very modern build with irregular shapes, bay windows, flat roofs, chimneys and lots of glazing would have cost considerably more and it also would have looked out of step with the countryside surroundings.
Due to this saving, we felt we could spend more on the interior which is why we have chosen to go with the higher end suppliers in terms of the kitchen, stairs and MVHR.
We have also been able to save money by getting several quotes from different suppliers and keeping them competitive against each other.
There are also several jobs which we have done ourselves particularly in relation to the airtightness which can deliver a good saving.
It’s very likely we will have to make some tougher decisions later in the build when it comes to bathrooms, tiles, flooring and furniture, and we will have to look at the more budget friendly options for them.
Kitchen and bathroom design
The kitchen was one of the easier choices on this build as we both wanted our kitchen to come from a local company that has a reputation in the Tyrone area for producing high end handmade kitchens. It was important for us as it’s a room we are going to spend the majority of our time in as a family, and when we visited their showroom we were sold straight away.
In fact, they were our first port of call when we got planning approved. We actually spoke to our kitchen designer before we spoke to our architect as we knew it was going to be the centrepiece of the entire house, so we basically got the kitchen we wanted and then designed the rest of the house around it.
I would recommend speaking with your kitchen designer alongside the architect at the very early stages of the design process as it’s such an important room in any house to get right.
As we are going for a very simple, uncluttered design with no stove or chimneys in the open plan kitchen/living area the room could look quite empty, so we really wanted the kitchen itself to be the standout feature of the entire house and give it the ‘wow’ factor. The kitchen designers gave us some really good ideas of simple features to add to really make it stand out, such as a bulkhead feature surrounding the entire room with upstand strip lighting and coving incorporated. For a small bit of additional cost it really gives the room a huge lift.
The bathroom choices at this stage are still up in the air. We have spoken to some local companies and looked at importing from Poland but haven’t fully settled on anything yet. Broadly speaking we haven’t focused as much on our bathrooms as they aren’t as high on our list of priorities.
Whereas in our kitchen/ living and utilities we have been meticulous in the details we want, we would be happy with almost any type and style of bathroom.
Designing the outside space
The outside space was at the forefront of our thoughts and was probably the second most important consideration for us after the kitchen/living area.
We really wanted the house to be absorbed into the existing landscape as we like the look of livestock grazing in the fields around the house, which is why we chose to go for no gardens at the front or sides.
We plan to only have an artificial grass area out the back so the kids can play on it all year round. From experience in our current house, the kids can only play in the garden a few months a year when it is dry. And they also bring a lot of muck and dirt back into the house which we wanted to avoid.
This option will be very low maintenance and we hope to offset the cost of this artificial grass by the fact we won’t have to buy any equipment to maintain natural grass (lawnmowers/strimmers/hedge cutters, etc.) which can be costly and time consuming.
Choosing external finishes
We deliberated for weeks over the external finishes and eventually settled for a sand and cement rubbed up finish. We both really like the look of a low maintenance acrylic render when it is freshly applied, in white. But we have seen too many examples where it gets really badly discoloured over time and turns green and black, which was off putting particularly as we are surrounded by trees and shrubs.
We also looked at a dashed finish as it would help to hide any hairline cracks which might appear but didn’t think it would suit the style of the house. We will eventually paint the house, but for now the grey sand and cement finish looks good and it also feels a little more like a blank canvas. It gives us time to choose the right colour.
Choosing windows and doors
The windows and doors were a relatively simple choice in terms of the supplier as the company we chose has a great reputation in the Tyrone area with excellent after sales support which was very important to us.
I was keen to go with triple glazed casement windows to keep with the passive house principles, but my wife really liked the sliding sash windows which only come in double glazed, so it was a trade-off between performance and aesthetics.
We eventually went with the double-glazed sliding sash as we felt that aesthetically it went with the house style better, and we were happy to take a slight hit on the U-value and airtightness.
We also knew that the windows would be expertly fitted and have also been told that a well fitted double glazed window will outperform a badly fitted triple glazed window.
To make up for a slight performance drop with the windows we decided to go for a composite door over the conventional uPVC as it had a better thermal efficiency and U-value.
We also tried to maximise south side glazing for solar gain, but we also wanted to try and keep some symmetry between the two gables. So, like many of the decisions it was a three-way trade-off between performance, cost and aesthetics.
Securing planning permission
Planning permission in this case was relatively straightforward as there were favourable factors which helped the site get approved. We applied under policy CTY 10 ‘Dwelling on a Farm’ as we knew we met the criteria for this policy. The house is visually linked to an existing farm building, and it has a very mature hedgerow fully surrounding it which meant it was an ideal site for absorbing a new dwelling.
There was also an existing laneway and excellent visibility splays in both directions from the entrance, so it ticked a lot of the required boxes. Our architect submitted the planning application on our behalf and dealt with the entire process which all ran very smoothly. The entire process took around six months from the initial application.
In NI, if your house is under 250sqm there is a fixed Building Control inspection fee of £238. If you go over that value even slightly, the inspection can rise massively into the thousands so it’s an important thing to consider when applying for planning permission.
Heating system choice
We went with a 12kW heat pump and underfloor heating on both the ground and first floor. The company supplying the heat pump sized this system for us, and although it is slightly oversized it has a variable control feature. This means that if it only requires 2kW, that’s the energy consumption it will use as apposed to coming on and off with the full 12kW blast.
It also means that the heat pump will never be running at its maximum capacity which will help with the lifespan of the compressor unit.
We have also installed photovoltaic (PV) panels on the south facing garage roof to complement the heat pump. The solar panels generate electricity, which is what the heat pump runs off. We also opted for the upgraded inverter which can incorporate battery storage.
At this point, purely from a cost perspective, we didn’t add the battery storage, but it’s nice to know the system is futureproofed and can be added down the line.
We always wanted the house to be ecofriendly and we are hoping that with high levels of insulation and good airtightness that it will be an economical way to heat the house also.
The other option we looked at was an oil boiler with radiators spread throughout the house. This didn’t appeal to us as we felt the heat pump in conjunction with the MVHR system would give us the best comfort levels.
There were lots of different heat pump options and to be honest they all were very good, but we got a recommendation from a friend who had installed this type of heat pump in their new build and that swayed us to go with that option.
We also looked at possibly upping the size of the hot water cylinder to 500 litres to take advantage of the solar panels in the summer, but we felt what you would gain in the summer you would lose in the winter with the bigger tank, so we eventually settled for a 300 litre tank. We used the rough calculation of 50 litres of water per person to size the cylinder.
Ventilation system choice
This was a choice we deliberated on quite a bit. We were always going to install a full MVHR unit as opposed to positive input ventilation (PIV) units but there was so much choice, it took time to get our heads around it. There were some budget friendly options, but we decided to spend a little more and go with one with additional features which we felt justified the uplift in cost.
The main thing we liked was the built-in preheater with frost protection. And the fact that it was self balancing. We had spoken to other friends who had installed MVHRs who were happy that they were getting clean fresh air but they said the temperature of the air was too low.
My advice in this area would be to double check that you have some kind of pre-heater/frost protection on the intake as otherwise on cold nights in winter your system will either not work at all or will be exhausting warm air and taking in much colder air.
For example, if your house is heated to 20degC in winter and the outside air temperature is zero degrees, with the MVHR running at 75 per cent efficiency it still means that the supply air is coming in at 15degC. That would be noticeably uncomfortable. With a preheater on the intake, the supply air gets a boost before it goes through the MVHR unit.
Provisions for on site electricity, water
I would recommend taking time to think of where the connections for electricity and water will go as it can add considerable cost if you must install transformers and several electricity poles. With the water connection also, we have heard some horror stories of sites being a longdistance from a connection point and ultimately having a massive drop in water pressure by the time the water reaches the site.
We have just recently got our electricity connected and bar the initial upfront cost of a new connection the rest of the process has been straightforward. From the moment we made the payment to NIE Networks, we had about a 10-week turnaround time to installation.
We were lucky that we had an existing transformer and pole just less than 200m from the site, so we didn’t require any additional infrastructure and we were able to run he cable underground. As the cable was running through agricultural land it had to be buried 1100mm deep which meant a little extra work on the excavation and back fill as the standard trench depth is usually 550mm. Thankfully my family owned the agricultural land we were digging through so there was no issue with permission or access. The water connection was made with NI Water and again the process was straightforward with a reasonably quick turnaround time. We had a new connection point about 100m from the site which means we have good water pressure.
Construction drawings
The more information you can bring to you architect at this stage the better as you can make more informed choices about the layout and style if you know what you want from the start.
Our construction drawings took some time and there were several revisions from the initial draft. We were lucky to have a good architect who was happy to listen to what we wanted and make suggestions and improvements.
We also took the initial construction drawings to several of the key people who would be working on the job such as the kitchen designer, MVHR designer, tradesmen, plumber and electrician.
They all were able to make slight changes and improvements and it was worthwhile speaking to as many people as possible at this stage as they all had good suggestions.
Explainers
Form factor: The relationship between the external surface area (A) and the internal Treated Floor Area (TFA). Achieving a heat loss form factor of less than three is a rule of thumb when designing passive house homes.
Compact building (low A/V ratio): A low external surface area (A) to internal volume (V) ratio – less than 0.7sqm/ m3 – will result in a more energy efficient build, i.e. one with a low heating demand.
U-value: A measure of how effective a material is as an insulator. The lower the U-value the better.
Airtightness: A measure of how many air leakages a building contains.
PIV: Mechanical ventilation system that pumps fresh air into the home, usually to a central location, to create a pressure differential that pushes out stale air through gaps in the fabric and trickle vents.
MVHR: Centralised mechanical ventilation system that mechanically extracts stale air and replaces it with filtered fresh air that’s been prewarmed (by the heat gathered from extracting stale air).
Costings
House build cost: £100/sqft
Building concrete blocks: £3.50 per square foot plus £9,200 for builder
Windows and doors (house and garage): £19k
Attic roof trusses (house and garage): £9k
Slates (house and garage): £8k
MVHR installed: £6k
Heat pump, cylinder and underfloor kit: £9.5k
Stairs: £4.5k
200mm blown bead insulation (house only): £4.3k
Electricity connection: £6.5k
Water connection: £1.2k
Electrical work: £9k
Cork Plaster
Even though it’s more expensive, Patrick chose cork plaster instead of traditional gypsum as it improves the thermal performance of a wall and allows it to breathe and balance room humidity which prevents condensation and mould. It’s also up to 10 times more elastic than traditional plasters reducing the risk of cracks and helps reduce thermal bridges.
Spec
Walls: 200mm cavity walls pumped with EPS beads, cork lime plaster on window reveals, U-value 0.17W/sqmK
Roof: 200mm rockwool between joists, 50mm insulated plasterboard below, U-value 0.12W/sqmK
Floor: 50mm insulated liquid screed to cover pipework, 100mm PIR board 50mm liquid screed on top (200mm total), U-value 0.15W/sqmK
Windows: timber sliding sash double glazed, overall U-value 1.4W/sqmK
