Cookies on

By continuing to use you accept the use of cookies.

Cookie Politicy uses cookies.

A cookie is a text file that is saved on your computer or mobile device, so that the website can identify you the next time you visit

Cookies are small files that cannot spread computer viruses or in other ways cause damage.

The purpose of cookies is to help websites identify users in order to provide them with the best possible experience of the site. uses the following types of cookies:

Session cookies:

A session cookie identifies you as a user during the time that you spend on the site. This cookie is deleted when you close your browser.

Analytics Cookies: uses cookies from Google Analytics. Google Analytics is a tool for measuring website traffic, which Rationel uses in order to collect usage statistics about, which pages and features are accessed by users on As a user you can opt out of Google Analytics cookies here:

Cookie Accept:

When you accept the use of cookies (either by clicking accept or by continuing to use the site), a cookie is saved with this information. Thereby you will not be presented with the cookie policy the next time you visit the site. This cookie is saved for one year.

Can I avoid Cookies completely?

Cookies can be completely removed from your computer and disabled in your browser. How this is done depends on which browser you use.

Extensive experience with Passive House

We have experience of various building types; domestic, residential and refurbishments, all to Passive House standard. You can get inspired and read more about some of our cutting-edge projects on the menu on the left.

Passive House solutions with Rationel Windows

We have extensive experience of Passive House Projects, and can provide specialised technical assistance and advice to support your organization from conception through to the installation of our products, helping you meet your design brief.

We can also advise on how to optimise the window design and glass solutions for different elevations. To give you the best results we offer to fine tune the window part of the PHPP calculation - after walls, floors, roofs and technical data for heating/ventilation have been entered into the PHPP.

Please note

The window guidelines for Passive House are guidelines only, while the criteria for heating demand (15 kWh/m2/year), air tightness (0.6-1) and the primary energy demand (120 kWh/m2/year) are mandatory.

We have optimised our windows according to energy balance; this typically results in a higher heat gain then heat loss through the windows. This enables you to utilize the free solar heat and thereby dramatically reduce your heating demand.


Be aware that using windows with the lowest Uw-value does 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.


To achieve the best results we recommend that the windows are optimised according to orientation and shading conditions. South-facing windows have the greatest potential for heat contribution, followed by west and east. North-facing windows will contribute with daylight, but are not thermally cost efficient.


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 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 isn't made then the final PHPP calculation will be defaulted into the conservative psi-value of 0.04 W/m K.

  • Rationel Vinduer Ltd.
  • 2 Bridgecourt Office Park
  • Walkinstown Avenue
  • Dublin 12
  • Phone 1800 292929
  • Legal disclaimer