Fakro L-shaped windows win race for Passivhaus modular construction

The latest eco-projectto which FAKRO has supplied roof windows is the Green Unit®, a modular, single storey Passivhaus design for a variety of sectors and the result of over three years prototyping and development. The prefabricated buildings are carbon neutral, FAKRO FTP U5 non-vented, triple-glazed windows with a U-value of 0.97W/m2K having been used individually and in L-shaped configuration. The L-shaped principle incorporates an additional lower window, in this case FAKRO BDR tilt and turn, to take the glazing area into the wall.  The FTP U5 windows have been installed in a green roof, those with an easterly aspect also having AMZ external awning blinds to offset solar gain.

The Green Unit’s Jonathan Finnerty commented, “The requirement to be carbon neutral meant that procurement for every element was considered in great depth. Fakro worked with us to achieve what we required and gave us highly valuable advice.”

The Green Unit is founded on deep ecological and ethical principles which influence every process, from design to final build. Off-site manufacturing in construction has long since overcome prejudices based on the sub-standard insulation quality of post-war prefabs. The common factor between that era and this, however, is the acute housing shortage but unlike 70 years ago, components and design are now the primary guarantee of quality, reduced lead times and lower cost.

Triple glazing is a prerequisite of Passivhaus construction and the availability of a choice of triple-glazed and non-vented roof windows provides added thermal efficiency and airtightness. FAKRO uses warm spacers between panes to reduce cold bridging through the envelope while TPE seals guarantee retention of flexibility and dimensional stability. Cold bridging not only allows heat to escape, but causes condensation, mould and overheating in the summer, the cumulative effect being to compromise the living space environment. The level of airtightness prevents air movement, traditionally a major cause of heat loss particularly in building using static roof window vents.

The barrel-vaulted design exemplified by the Green Unit is an illustration of a highly contemporary design tested to achieve Grade A/A under SAP testing and Level 5 of the Code for Sustainable Homes. FAKRO roof windows can go further than the FTP U5, their quadruple-glazed FTT U8 Thermo offering an installed U-value of 0.58W/m2K.