We sealed the window openings of the Kilcloon Passive House with OSB board and did the first airtightness test today with a result of 0.56ac@50kP without membranes or tapes just silicone. We found it much easier than using tapes and membranes, there were 2 guys on site for 2 days after the timber frame was erected so we think we saved close to €5k in time and materials by using this method. We used tongue and grooved OSB for the roof with silicone in the groove and this was tight as a drum.

So thanks FTom for the idea for sandwiching the silicone between the rafter and OSB.

Silicone in the groove! We’re convinced now of this method and will use it in future, our builders love it because they’ve been through dishearthening airtightness tests before trying to do it from the inside using membranes/tapes, often getting the same result in the evening after a days work. So next step is to try to get it down a bit forther and maybe go for the Irish record of 0.15 and then fit the windows next week. All the plumbing and electrics will be done without touching the airtightness layer and all services come in through the slab.

Air Heating; We used compacted 804 stone (with fines) to fill the Solar Slab, if we used clean stone we could have put a few air vents on the perimiter of the Solar Slab and sucked air into the building which would filter through the stone (getting heated up along the way) so we could have vents in the middle of the house with fans attached sucking in fresh air that was heated by the Solar Slab.

Is the slab going to be hot enough to produce hot water, even at the worst time in the annual cycle, or are you going to need a (backup?) heater for hot water? The difficulty I always have with solar seasonal storage is that it seems to make no sense to me to design a system to cater just for space heating. Since you have to have some heating system for hot water, you might just as well increase its size a bit and do away with the seasonal store. And if you try to build a seasonal store for both space and water heating, it gets quite large with high requirements (temperature, potable water legalities etc).

To avoid using a back-up heating system we are using a “Solar Slab” http://www.viking-house.ie/hydro-thermal-energy-store.html , 8m2 of Solar tubes will heat the 90m3 “Solar Slab” within the foundations to 60 degrees. The store is insulated from the house with 100mm of insulation to slow down heat escaping. The store is designed to emit 2kW/hr/day and to store enough energy for 100 days heating. We’ll start charging the store towards the end of August and stop charging the store in May every year to avoid overheating. Excess summer heat from the Solar Tubes will be dumped beneath the ground insulation, we aim to increase the temperature of the soil beneath the house to 25 degrees or better.

We will use the “Warm Stud” timber frame method to avoid membranes or tapes http://www.viking-house.ie/timber-frame-warm-stud.html We will use silicone squeezed between the plywood and the rafters as the airtightness layer.

We will use FiWi HRV http://www.viking-house.ie/fine-wire-hrv.html to avoid the use of HRV ducts.

These were our first 2 full roof’s, but there are a number of builders using the method around the country with each one inventing their own solutions, so its an evolution!

We used 9mm OSB on a smaller extension roof and the roof felt too bouncy which could lead to joints opening and putting in the extra noggins at each joint was quite a bit of work, on the same job we were using T&G OSB on the first floor which felt really sturdy, so for an extra €800 we used the T&G OSB for the roof as well and we’re delighted with the result.

I felt that the “bubble glue” was a bit rigid and allowed for less movement when it set and its easier to see which joints are sealed when you use white silicone, but I have nothing against “bubble glue” in principal!
I used to repair furniture and I always found the “bubble glue” difficult to get off my hands!

I have to think about your galv angles and flatstrap method but it sounds flimsy if I understand it correctly, would it resist the weight of a roofer standing on a 9mm sheey near a joint?

The T&G OSB sheets are joined horizontally at the rafter and vertically at a joint. The 15mm T&G OSB sheets cost us €17.50 per sheet and €7/sheet for the 9mm standard, maybe cheaper 12mm T&G sheets are available?

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Some calculations for Steamy Tea!

This bungalow has a 90m2 Solar Slab while the 2 storey house has a 55m3 Solar Slab and compacted sand/gravel can store 40kWh/m3 I’m told. The PHPP says we need 1,750kWh to heat the bungalow for a winter and 2,000kWh for the 2 storey house so it will be interesting to test them out next winter, both clients have agreed to use an electric fan heater as a back up which is great.

Viking House

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