Saturday, February 26, 2011

Belfast Passive House construction methods and materials used

The GO Passive house is situated in Belfast, Maine, USA; the development is the first certified Passive house in Maine and the twelfth Passive house to be constructed in the entire United States. The dwelling was a model for a 36-home eco-village that began construction in spring 2010. The Geological Prototype home was a design and build collaboration, with the aim of achieving a 1500 sq/ft super energy efficient home that uses 90% less energy compared to conventional buildings. In recent years Ireland's weather patterns are quite similar to those seen in Maine, where winters are very cold with severe frosts occurring and summers providing occasional heat waves, this is why I feel that some of unique details and construction methods used in the GO Passive house to achieve the required thermal performance and also keep the price at affordable levels could potentially work in Ireland.  

The Slab on Grade foundation system was used in the Belfast development, where a compacted gravel base was installed then a sand and concrete flow-able self levelling mixture on top of this base was poured. A layer of high density insulation was then installed running approximately two foot outside the house boundary to hold the heat in during the winter months. This high density insulation is the material upon which the Insulated Concrete Form (ICF) footings bear on, this provides a complete thermal and moisture break between the concrete and the footings to ensure the dwelling will be isolated from the ground. The ICF prefabricated formwork comes in clip together sections which hold the rebar in place. The services/utilities entrance area includes the water line, electric cable, sewer outflow pipe and heat sensing probes to monitor the septic area and under-slab temperatures for the geothermal heating system, this is sufficiently sealed with expanding foam. There are two peeks tubing pipes entering the services inlet, one is buried and run at 5 foot below the ground with the water line for convenience, and the other pipe is inserted in the sewer pipe, as a lot of warm water exits the building into the septic tank, this provides the pre-heat for the heat recovery ventilation system installed.
An 8 inch layer of rigid insulation is placed on the internal surface, with a layer of plastic also added that acts as a vapour barrier and is run up the walls. Once the footings were cast the pressure treated mud sill or wall plate was attached and then a second plate added so the structural insulated panels (SIP) which consist of orientated strand board on both faces with a foam centre, could be easily installed. The SIPs were pre-cut in a factory in Vermont, the 4" wide by 24" long panels slide and lock systems means accuracy, speed of production and speed of construction was achieved which in turn reduced labour costs. The panels were attached, to locally sawn white pine timber frame 6 inch x 6 inch beams which were attached beforehand to the foundation with steel brackets and bolted and plated together, which was all subsequently sealed with caulk to ensure no air leakage. The panels were installed with an intentional vertical void left internally so expanding foam spray and the external surface of the panel connections was primed to remove grit so the insulated tape could be attached sufficiently.                               

The triple glazed tilt-turn windows were imported from Germany; with a pine wood frame and an aluminium clad exterior finish which conducts energy. There is an Argon gas between each layer that provides excellent thermal performance and the insulated glass optimises solar gains with a 60% acceptance ratio and reduces heat loss which has a low e-coating that increases the energy insulation of the windows. The external finish is a board and batten effect and the roof is a metal clad.


  1. Good analysis Martin. Very surprised in reading that the first Passive house in Maine was only constructed in 2010. From the photograph the building in my opinion looks quite different to a traditional building, it looks very much like many would imagine a passive house to look like. What do you think? Maybe the fact that a passive building can look the same as a traditional building should be advertised more in the Irish market?

  2. Surprisingly enough alright Luke, But as stated it is the first "CERTIFIED" Passive house, there is probably a few dwelling constructions in the locality built near passive standard but are not certified, defined as ecological buildings or green buildings.
    Defiantly does not appear like a traditional Irish building from the photograph, but I suppose there is room for fresh structural appearances in Ireland, maybe an incentive for clients to change the style, the fact that this building is able to survive the harsh climate conditions in Maine, means it should be suitable to Ireland.
    GO homes are passive developers like Viking homes, and similarly have a set number of achievable passive designs, I suppose there defiantly would be room for improvement from a design perspective.

  3. Hey Martin,
    Very good example due to the climate similaritys with Ireland. At 140 m2 it is bigger than the Denby Dale Passive House (118m2)on which I did my blog. Different construction methods are also used. Just some questions...

    1. Is there any issues with thermal briging around the services/utilities entrance even though it is sealed with expanding foam?

    2. How is the roof insulated ? and does the metal cladding retain heat sufficiently?

    3. Is there any thermal briding problems with the steel brackets to which the locally sawn white pine timber frame 6 inch x 6 inch beams are attached.

  4. To answer question 1:
    There is no issues regarding thermal bridging around the services/utilities entrance as the entrance is 8 inches of insulation and a vapour/air barrier forming a sealed environment, the entrance is entering the building through a plastic services pipe and has been sealed with a cock joint, an adhesive back membrane to create an air barrier.
    To answer question 2:
    The video above give a guide to how the roof is structured to maintain sufficient heat levels.
    To answer question 3:
    There is a no problem with thermal bridging as the structural insulated panels are placed on the external face of the beams, the locally sawn white pine timber frame 6 inch x 6 inch beams are anchored through the plastic and into the footing, with the gaps in the plastic air barrier sealed by caulk. There is a cellulose insulated 2x4 stud wall, where wiring is run, with a 6 and a half inch panel on the internal face, so the beam will be placed between the two insulated panels.