Introduction:
Ireland's most airtight house was constructed in Co. Wicklow by Jer and Jackie Rynhart.In 2003 Jer and Jackie Rynhart bought an old school house near Rathangan in the hills of west Wicklow. They considered renovating the old school house but Jer reasoned that if they wanted the best build possible, they should start from scratch.
The Rynhart’s decided to go with a timber frame construction design, where they approached several timber frame companies before choosing Wexford based Shoalwater Timber Frame, who Jer praises for their “wealth of knowledge”, inventiveness and attention to detail.
Super- insulated envelope:
The house features an Isoquick insulated foundation, which is essentially an EPS formwork around and below the concrete slab. The foundations consist of a 250 mm concrete slab with 300 mm of polystyrene underneath and 150 mm around the edges so it is completely insulated on all sides. The system comprises of edge modules and deck modules which come in different thicknesses depending on the thermal requirements, also the different thickness of deck modules allows the thickness of the concrete to be varied depending on the structural demands. This system provided the ground floor with a U-value of 0.11 W/m2K.
Shoalwater then erected the timber frame which was insulated on site. The walls feature 80 mm of Gutex Ultratherm wood fibre board externally, inside the outer Gutex layer is a Panelvent which is a diffusion open external sheathing board which provides structural racking strength and wind resistance, 220mm of cellulose insulation in the stud plus a 100mm service cavity insulated with Gutex Thermoflex, Fermacell boards made from gypsum, cellulose and water line the walls internally. This wall design provides a U-value of 0.11 W/m2K.
Gutex uses a tongued and grooved system for fast construction which can be seen in the above picture.
The roof construction consists of 310mm of cellulose insulation and 100 mm of Gutex Thermoflex. The roof has a U-value of 0.11 W/m2K.
Ecological Building Services supplied many of the green material used in this build and engineer Niall Crosson says that the primary advantage of using Gutex Ultratherm externally was to increase the thermal mass of the construction, while putting a significant proportion of the insulation to the outside of the frame to reduce non-repeating thermal bridges.
Ecoglaze supplied the windows, triple glazed Internorm Edition with an overall U-value of 0.79 W/m2K.
Ground Breaking Airtightness:
The most impressive aspect of Rynharts house is the airtightness. Intello Plus ‘intelligent’ membrane was used troughout the walls and roof just inside the main cellulose insulated cavity which provided the air tight envelope and vapour diffusion layer. In Winter Intello plus is highly resistant to diffusion and thus protects the building structure, however, in Summer it becomes up to 50 times more vapour permeable allowing the vapour that may have entered the building to dry out.
Pro-Clima’s Solitex plus wind tight membrane was used in the roof, taped and sealed with wind tightness tapes. It is completely air impervious yet has an extremely low vapour resistance to maximise vapour diffusion to the outside.
The most recent airtightness test performed produced phenomenal results of 0.15 air changes per hour (ACH) and a Q50 figure of 0.19 m3/hr/m2. The Q50 figure is the best Construct Ireland has ever published.
Space heating:
Jer Rynhart is so confident in the thermal performance of the build, he is not installing central heating, although he is considering electric underfloor heating in the kitchen. The space heating will be provided through the ventilation where he is planning to install a Genvex Combi L-S unit which can provide both space heating and hot water. This system is certified by the Passive House Institute. Domestic hot water is provided from the 185 litre tank which has heat pump priority and can be supplemented by solar or other heat sources through the internal coil. The Rynharts are installing solar thermal, Solar Focus CPC system and and are considering solar PV and wind power into the future.
Conclusion:
The attention to detail during this build was very impressive and an outstanding airtightness result was achieved. Rynhart even put Pro Clima Elasto tape over the staples used to attach Pro Clima membranes in the wall and roof. Niall Crosson from Ecological Building Services says this isn’t necessary to achieve passive airtightness levels but says Rynhart was keen to see if it made a difference nonetheless. Airtightness before taping the staples was 0.22 ACH and after it was 0.15 ACH but other holes were found in the intervening time so Niall Crosson reckons sealing the staples made negligible difference.
The airtightness of this house is very impressive and that is down to the attention to detail and careful workmanship through out the build but I would be interested to see a feasibility study done on the house to determine if the almost fanatic attention to detail resulting in extra time, labour and product costs are economically worth while compared to if the house was still Passive but achieving airtightness closer to 0.3 ACH.
Great post John, very interesting summary.
ReplyDeleteAs you said i'm not too sure that all the extra work to get the house so airtight is worth it. I think as with everything you can over do it, and maybe that level or airtightness is overkill.I wonder does halving the amount of air changes needed have any affect on the air quality in the building or would it cause the HRVS to run at a higher output to achieve 0.3 air changes per hour? Does it really make the house more economical?
I enjoyed reading about the construction methods because they are very similiar to the methods I have used in our project so its nice to see it being used in real life.
Jan.
John,
ReplyDeleteAs you referred to, the airtightness is fantastic but taping over the staples does seem too much. One wonders if this will effect energy costs as time goes on. Hardly, I'd imagine.
The Genvex Combi ventilation system which provides space heating and hot water supply is a good idea. I see from looking at the link that it still allows the option for the hot water cylinder to connect to another heat source e.g. solar panels. This gives peace of mind to the owners should the ventilation system under perform (although it says it can reach an efficiency of 95%, which is impressive).
Good, informative post.
Shay
Hi lads,
ReplyDeleteThanks for your comments. The air tightness on this house and how it was achieved does seem excessive.
I agree with what you are saying Jan it would be interesting to find out if this low air change rate effects the air quality in the house or make the ventilation work harder and cost more to run. After the effort and workmanship that went into the build it would be a shame if windows needed to be opened to ventilate the house.
Shay i agree the Genvex Combi boiler appears to be a efficient reputable boiler which can provide hot water and space heating and importantly is certified by the Passive House Institute.It seems to be good boiler and as you said can be supplemented with renewable heat sources such as solar panels or wood pellet boiler.
Regards
John