What is the definition of a “Well-Sealed Ceiling”?

BS 5250:2002 AMD1 defines a well-sealed ceiling as follows: The design avoids constructional gaps, especially at the wall ceiling junction with dry lining construction, and holes in the ceiling. No access door or hatch should be located in rooms where large amounts of moisture are produced, including kitchens or bathrooms. The air leakage rate through an access hatch, including its frame, when tested to BS EN 13141-1:2004 4.3 is less than 1 m3/hr at a pressure difference of 2Pa. It can be assumed that “push-up” wooden hatch covers in a frame, constructed in-situ, with continuous compressible seals, will meet this criterion provided the weight of the door is at least 5.5 kg.

Hatch covers should either be heavy enough to compress a seal or be clamped, with closed cell compressible seal, or “o-ring” between it and the frame. Drop-down hatch covers are more difficult to seal; it is recommended that propriety units with a supplied hatch cover in a frame are used. Manufacturers can provide third party evidence that the leakage criterion is met.

Penetrations, such as those for services and rooflights, are permanently sealed with suitable proprietry products. The ceiling is sealed to the external walls to limit any leakage through cracks. Recessed light fittings should comply with BS EN 60529 and be rated IP60 to IP65 (depending on room use), or incorporate an appropriate sealed hood or box which meets the following test criteria.

The total leakage through downlighters should not exceed 0.06 m3/h.m2 of ceiling at 2 Pa. The head of all cavities in the external walls, party walls and partition walls is sealed to prevent transfer of warm moist air into the loft.

 

What is the definition of a “Normal Ceiling”?

Ceilings where no particular attention has been paid to securing the airtightness of the ceiling. No attempt is made to fill hidden cracks (in cupboards, behind kitchen units, etc.) and penetrations through the ceiling by cables and pipes.

Typically the airtightness of buildings in the UK have been measured at about 12 to 14m3 / m2 / hr. The target figure for the UK is 10 m3 / m2 /hr, whereas, the rest of Europe are achieving 3 to 5 m3 / m2 / hr

What are the definitions of “Cold” and “Warm” roofs?

A cold roof has the insulation at the horizontal ceiling level and usually a large void or space between the insulation and the pitched roof rafters.

A warm roof has the insulation at the rafter level. This is usually to provide usable living or storage space.

 

 

 

 

If I am using vapour permeable underlays (VPU’s), do I need any further ventilation?

In the vast majority of cases, Yes!... This is because air movement through the tiles or slates cannot be relied upon for the life of the roof. All ‘Cold Roofs’ need some additional ventilation (whether it be eave or ridge or a combination of both). Most ‘Warm Roofs’ need some additional ventilation (unless built specifically for a ‘simple’ roof, and to a high integrity with VPU’s and well-sealed ceilings).

 

 

 

Does the Thysis product infringe the Ubbink patent?

No, it does not. Thysis asked Ubbink to consider this question, and in the summary they concluded that

“…we acknowledge that the Patent is not infringed by your Product. This includes, without limitation, acts of manufacture, disposal, offers of disposal, use, importation and Keeping (for disposal or otherwise).”

For the full statement, you can click on the following link: (Ubink Statement)

 

 

 

What is the advantage of using the Thysis OVEP rather than the Ubbink OFVS?

There are several!

• The OVEP comes in convenient 1m lengths and has a cover width of 200mm (rather than the 0.9m and 150mm of the OFVS).
• The OVEP has the unique ‘split skirt’ feature that makes the process of gutter installation much easier.
• The OVEP has an ‘easy fit’ overlap rather than the over complicated ‘tongue-and-grove’ connection on the OFVS.
• The OVEP has engineered nail/screw ports with ‘sleeves’ into the centre of the fascia edge.
• The OVEP has a 25mm nail guide height (rather than the 15mm on the OFVS) which removes the need to cut the fascia board – simply use the next size down!
• The Thysis BC is designed to fit with the OVEP, allowing a simple 2-in-1 to 3-in-1 conversion.

What is the benefit of using ‘Over Fascia’ rather ‘Soffit’ vents?

Using ‘Over Fascia’ vents means that plain soffit, rather than vented soffit board can be used, which reduces the overall product cost. Also, vented soffit boards and circular soffit vents soon get covered in highly visual dust, grime and cobwebs – which is not the case with ‘hidden’ Over Fascia vents, giving the property a significantly improved “kerb appeal”

 

 

What are the advantages of using the Thysis products over other ‘Over Fascia’ products?

For the main features and benefits of the Thysis products, please refer to our literature: (Thysis leaflet PDF)

In summary, the Thysis “Over-Fascia Vented Eaves Protector” (OVEP) and made-to-fit “Bird Comb” (BC) make the installers job significantly quicker and easier than other systems available. The OVEP combines Eaves Protection with Eaves Ventillation in a purpose designed product. The unique installation benefits and ‘split skirt’ feature also allows the ‘downsizing’ of fascia board and makes the fitting of guttering easier

What increases the risk of condensation?

A number of factors in modern construction, including:

• The increased use of high-performance draught-proof doors and windows.
• Modern lifestyles generate higher amounts of water vapour.
• Average air temperatures, and hence water vapour within buildings, have increased.
• Increased amounts of insulation at ceiling level have led to colder roof voids.
• Use of roofing underlays has greatly reduced the natural ventilation of the roof space.
• The misuse of vapour permeable underlays (VPU’s), often with sealed laps and with no loft insulation at all.

 

Why ventilate the roof?

Roof ventilation is essential to combat condensation in the roof space. Condensation can cause serious damage, including severe structural weakening by dry or wet rot, loss of effectiveness of insulation, and damage to decoration through staining and mould growth.

 

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answers to commonly asked questions