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9” Hollow Blocks FAQ

What is a cavity block?

Cavity blocks, sometimes called 9″ inch hollow blocks, were sometimes used for the construction of dwelling houses and are particularly common in the Dublin area. Dimensions are approximately 18 inches long by 9 inches wide and 9 inches high. The middle of these blocks is hollow.

What is the difference between a cavity wall and a cavity block wall?

A cavity wall is constructed by building two walls parallel to each other,  using solid blocks and leaving a gap of three to four inches between them. The walls are not bridged anywhere and this eliminates the risk of water penetration to the inner leaf.

A cavity block wall is constructed by building a single wall using these hollow blocks and placing them on top of each other in a stag­gered manner.

What are the disadvantages of cavity block?

By their nature, a cavity block wall is bridged every seven to nine inches. Compared to a cavity wall, there is a higher risk of dampness, and mild mould growth appearing on the inner walls. This is particularly the case with older properties.

How important is wall insulation?

All houses built today have to conform with strict building regulations in respect of wall insulation. Specific U-Values have to be achieved to ensure adequate thermal insulation. However in the recent past houses have been constructed with no wall insulation and that can be quite problematic.

How can you insulate cavity blocks?

If you could look down from the top of a cavity block wall, you would see empty columns. By drilling small 18mm holes into each column and injecting urea foam, these columns can be successfully filled with high density foam insulation. This greatly enhances the thermal value of the external walls.

Will all the wall be completely filled?

No, because the blocks are bridged at fre­quent intervals. Approximately 20% of the wall is solid, therefore about 80% can be success­fully insulated. This can vary depending on the actual construction and the size of the cavity in the block which dif­fers with manufacturers, but even an 80% insulation fill will bring enormous and immediate insulation benefits to the home.

Will insulation eliminate mildew and mould growth?

While any insulation will help to alleviate the problem of mildew and mould growth, absolute assurances cannot be given. Normally condensation on an inner wall is caused by warm air meeting a cold surface, so if the wall is insulated to 80%, the risk of mildew and mould growth is greatly reduced.

Will my house be warmer?

Yes! Any building can be heated if the heat is on high enough and often enough. However the real test for energy efficien­cy is what happens when you turn the heat off. In an uninsulated house, you will find the building loses the heat very quickly, because there is very poor heat retention. A home with even 80% insulation will greatly enhance both the comfort levels and efficiency of your home.

How do I know the blocks are all filled?

The foam is injected in semi-liquid form and will flow like water, so that all voids and cavities are filled completely. The density is predetermined and the foam will not sink or settle after installation.

Why should I deal with Premier Insulations?

Premier Insulations is one of the oldest established insulation companies in Ireland. We have completed more than 10,000 insulation jobs across the country. Over the years, many competitors have come and gone, but our expertise and experience goes on. Contact Us to see what we can do for you.

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