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intelligent airtight systems

What are the advantages of a Wellhofer Attic Hatch & Sealing System? 

The Wellhöfer Attic Hatch features a certified airtight and pre-insulated attic door.  In addition, it also features an independent airtightness sealing system which Wellhofer Passive house attic stairs - certified componentseals the hatch frame to the surrounding timber joists, noggins or the adjacent airtightness and vapour control layer.  Both the hatch and
the additional hatch frame sealing system has received 3rd part airtightness certification.

The airtight seal of the hatch door is maintained by a pre-stressed spring, this ensures the door remains airtight even when a blower door test is conducted.  The spring is also fully adjustable which ensures the homeowner's requirements can be met.  

The airtightness of Wellhöfer 4D is 5 times better than that required by DIN 4108-2 and is certified to EN 1026:200-09.

To what extent will an insulated attic hatch improve the overall U value of the attic?

Leaving aside heat losses which may occur due to air leakage, if an uninsulated attic is installed, the U-value for an attic can increase from 0.16W/m2K to 0.18W/m2K. This is quite considerable over the surface area of a ceiling.

The Wellhöfer 4D hatch and ladder are ideal for both new build and retrofit projects. Wellhöfer 4D airtight attic hatch is supplied in a standard 1200x 600mm dimensions. A smaller certified airtight pre-insulated access hatch is also available (600 x 600mm).

The emissions levels of the Wellhofer attic stairs is over 9 times better than the value which is considered to be harmless as required by the Sentinel-Haus Institut

The formaldehyde value of the attic stairs is over 16 times better than the value which is considered to be harmless as required by the Sentinel-Haus Institut. 

Once the attic hatch is airtight, how do I seal the hatch frame to the ceiling airtightly?

There is a number of certified airtight attic hatches available on the market, but a key weakness in many attic hatches is that while the door may be airtight, air leakage may occur between the frame and the ceilings airtightness layer (i.e. the vapour control layer/membrane).

Wellhofer manufacture a 3rd party certified attic hatch which has a certified airtight door, and a certified airtight sealing system which seals the hatch frame to the adjacent airtightness layer of the ceiling (i.e. the vapour control layer). 

One may install an attic hatch which has an airtight door, yet, the leakage area between the frame and the surrounding noggin/vapour control layer can lead to a hole the size of an A4 page in the ceiling and an additional 70-100 litres of heating oil required per year! Therefore one cannot underestimate the importance of not only installing an airtight and adequately insulated attic hatch but also to ensure the frame is also installed airtightly.