Build Method

Foundations

For our foundations, we normally come up two rows of blocks (traditional blocks) and then we change over to using a QUINN lite block as a thermal break between the cold foundations and the finished floor. We use 150mm of high-density insulation broken up into an overlapping 100mm layer and a 50mm layer. The reason for this is to reduce the coldness coming up from the floor, as they over lap the joints. We use high-density insulation to get as much of a U-value in the floor while taking up the least amount of space possible. When we have the foundations and the insulation in we pour the finished floor.

Block Build with 200mm of EPS External Insulation

This is an alternative method to Timber Frame. 215mm concrete blocks are laid on the flat with 200mm of EPS insulation. Then a base coat is applied with reinforced fibre mesh. Another layer of base coat is applied. This is finish off with a breathable acrylic render. This will achieve a wall U-value of 0.15

Air Tightness

Air tightness means that we are reducing the drafts blowing through the building. By putting on the 1mm airtight layer we get to reduce the drafts blowing through the building but also the fact that we have it there it improves the insulations U-value by 30%. The reason is, if you use the analogy that if you have a woolly jumper on a windy day, the wind can blow through the jumper but if you put a 1mm jacket on over the jumper you’ll feel the warmth, as it stops the wind from blowing through it.

We use Siga as they are an established producer of tapes and membranes. They manufacture their own tapes and membranes in house and don’t sub contract out, which guarantees to us the quality of the product that we would be using on your home.

Then we put in a 50mm service baton over the airtight layer. This is where all the wires and the plumbing run, all the services are in this area. We want to minimize or eliminate any wires, pipes, cables, etc penetrating the airtight layer. The fact that we have the service cavity on the inside allows all the services to be on the inside envelope of the house and not the outside envelope of the house. This area also gets 50mm Rockwool flexi insulation. This now gives us an over all wall thickness of 300mm of Rockwool.

There is a rule of thumb, when you are fitting insulation in a low energy house, that you should never break the insulation up, that all the insulation must be together. Hence you can accurately calculate the condensation point in the wall. This is what is known as the 80/20 rule. 80% of the insulation must be on the outside of the airtight membrane and you are allowed 20% inside the membrane, which for us is our service baton. In our case, we place 95% of the insulation outside and 5% inside.

After we fit the counter baton we use OSB board on the inside. The advantages of using OSB board on the inside is that it gives good racking strength to the inside walls. It also helps for people who want to hang pictures afterwards as they do not need to find a stud, they can just screw it directly into the ply. After we fit the ply wood we fit the dry wall slab and the dry wall slab we skim it. This is the finished inside surface.

Ventilation

The ventilation that we use is called a manifold System. We use a manifold system, so we can control the volume of air going to each room individually. You don’t restrict the airflow on the room side; you restrict the airflow at the manifold itself. The advantages  are that you get less noise through pipes and that you are able to clean the piping afterwards. When it comes to cleaning them after 5 years it’s a simple process as we run individual pipes back from the manifold to each room.

The ventilations unit which we use, are the PAUL ventilation unit, or Brink Insulation unit.

In Ireland because we have very high humidity in the air the ventilation systems work quite efficiently as the humidity allows for the heat transfer a lot better than dry air. The down side of the high humidity is that we must have breathable walls. Going back to the wall structure that we have, we know that all of what we have done is breathable from the outside inwards. We go from a not so breathable wall membrane on the inside of the envelope to a very breathable wall membrane on the outside. This means that moisture is always looking to move outwards, and because we have a ventilated space between the timber frame and the block work it can evaporate away. If you change this and you use high density on the outside this would push the moisture inwards, thus it is not advised to use high density insulation in your walls.

Heating

When we are plumbing a house, whether it is for under floor heating or radiators, all the room get a wall stat fitted to a wall mid way up. That wall stat is then wired back to the manifold in the plant room. In the plant room we run the individual pipe work to each room. This allows you to control each room individually, so when you have a low energy house and you have south facing windows the room can be quite quick to heat up and if you turn on the heating for the other rooms that are cooler, then you will over heat the room unless you know have a way of turning off the heat to that room.

Having a TRV valve on a radiator does not work efficiently enough and does not react quickly enough. With a wall stat on the wall it controls an actuator at the manifold and is very quick to close that circuit off when it is up to temperature. Hence you could have 9 out of your 10 radiators on or just one radiator on, by using this manifold system. Therefore you are not wasting any energy heating rooms that do not need to be heated. This is something that we always do with our homes.

Windows

When you start to build walls of overall thickness of 462mm, with such a low U-value, (our walls have a U-value of 0.12) you need to really look at your windows.

If you put in poor quality windows into a wall structure with a u-value so low you could actually feel the coldness when walking past the window. Hence you must have a very good window. The

windows that we use are German windows made by NIVEAU. We use Niveau window because of the their high standard and quality. They have been manufacturing passive windows for the past 55 years, and their technique hasn’t really changed much expect for the glass. The glass quality has increased over time and now they offer triple glazed windows that are Argon gas filled. The window itself has 4 seals which is not common among Irish windows as most windows available on the Irish market have 2 seals. By this we mean that when the window open and closes it has 4 contact points with the frame, making it a very airtight window.

Fireplace

When your building an airtight home it is very important that the external air connection for your fireplace must come from the outside. When the fire is burning, on average, you would use about

40 cubic meters of oxygen per hour. If you were to take the air from the room, when you have an airtight house, there is a good possibility that you will very quickly use all the oxygen and feel very drowsy. Most fireplaces, in airtight house have external air connections. It is very important to have this connection done from the outside and not take it from the room, as when you build an airtight house you do not have airtight vents. If you were to buy a normal fireplace that does not take external air from the outside and you were then to put a room vent in the wall it would be like having a puncture in your tire. All of the air, because its under pressure, wants to escape out through the vent. Thus having the high U-value in the wall becomes redundant.

Eco Joist

On all our ceiling we run a counter batten and use eco joist web floor. The reason we use eco joist and not a solid joist is that when you have a ventilation system in the house it is a lot easier to run the pipes, cables etc. Other advantage of using a web joist is that it reduces the sound traveling through a solid joist to the downstairs.

Attic Insulation

In the roof space we always use 450mm Rockwoll Roll. We do this as this is the passive house standard and most of the heat is lost through the roof.

Plant Room

It’s very important to have a room big enough to carry all the plant in the house. A room, on average, about 2m x 2m is sufficient but bigger is better. When you build a low energy home you have lots of different cabling and piping coming back to the one area. In the plant room you have all the cabling for the power supply, switches, lights, entertainment, tv, alarm, data, solar pipes, upstairs/downstairs wall stat cables. Also the outdoor heating pipes 1" diameter returns insulated from where ever the boiler is gong to go outside to inside the hot press (Plant room), minimizes having any external joints on the outside and less change of a leak. There are also no joints from where the radiators are back to the hot press. It does require a lot more piping but you do not have any joints in the floor.