Extensive experience with Passive House
Rationel wish to be the best when it comes to energy-saving window
solutions and guidance. Therefore we have participated in a number
of cutting edge passive house projects. We gladly share our
experience, since windows have a crucial importance in terms
of reaching the heating demand for low-energy buildings. Our
experience includes various building types; domestic, residential
and refurbishment all to Passive House standard.
Read more about the projects and what the windows
contributes here.
Passive House solutions with Rationel Windows
We have extensive experience on Passive House Projects, and can
provide specialized technical assistance and advice to support your
organisation from conception through to the installation of our
products, helping you meet your design brief.
We can also advise on how to optimize the window design and
glass solutions for different elevations. To give you the best
result we offer to fine tune the PHPP (Passive House Planning
Package - the energy calculation program used for Passive Houses)
regarding windows - after walls, floors, roofs and technical data
for heating/ventilation have been entered into the PHPP.
Please note
The window guidelines for Passive Houses projects are guidelines
only, while the criteria on heating demand (either 15
kWh/m2 year or 10 W/m2 year), air tightness
(0.6-1) and the primary energy demand (120
kWh/m2 year) are mandatory.
We have optimized our windows according to energy balance which
typically results in a higher heat gain than heat loss through the
windows. This enables you to utilize the free solar heat and
thereby reduce the heating demand dramatically.
Be aware that windows with the lowest U-value do not necessarily
result in the best energy performance for the building as a whole.
Our experience is that 50% of the full heating demand can be
covered by solar heat gain though the windows.
Orientation
To achieve the best result we recommend that the windows are
optimized according to orientation and shading conditions;
south-facing windows have the greatest potential of heat
contribution, followed by east and west-facing windows.
North-facing windows will contribute daylight but are not
thermally cost efficient.
Installation
Installation details are often overlooked but in our experience
it is important to understand that a lot of heat can be lost here
(linear transmission loss - psi-value) if this detail is not
developed in conjunction with the overall building design. A
well-designed installation detail can typically cut down 0.5-4
kWh/m2/year of the heating demand - a significant
proportion of the total allowance of 15 kWh/m2 year (up
to 25%).
We
also have drawings of various installation
details suitable for Passive House projects with corresponding
psi-values. However, as these vary we would recommend that the
best solution is to have the exact psi-value calculated on the
project-specific installation details.
If an exact calculation is not made then the final PHPP
calculation will be defaulted to the conservative psi-value of 0.04
W/m K.