House Eco Refurbishment

USING SEMPATAP

SOME COMMENTS AND OBSERVATIONS FROM MARK MANSBRIDGE

I have just completed a project in insulating my small house in Lewes with Sempatap solid wall insulation and I would like to share some things I have learnt about the use of the product.

My house was built in about 1860. It has solid walls throughout and the north facing side- wall is one brick thick with some rudimentary panelling. Alterations dating from the 1960’s didn’t improve things much with fibre board added to some internal walls with a small cavity.

With only one brick between me and the neighbours, I was also interested in Sempatap’s claims as a soundproofer, especially with other solutions being considerably thicker.

Since installing Sempatap on the whole ground floor and the north wall stair well, I have noticed that the house feels considerably warmer and heat is retained for longer. With regards its soundproofing qualities, I can still tell when my neighbour has her TV on but I can’t identify the programme anymore.

HANDLING

I probably started off on the wrong foot by doing the fiddly cutting around stairs first whilst trying to learn about using the product. I quickly realised that you should only do short vertical runs as it slumps under its own weight if you go beyond say 6 feet. If it does slump it can crack across its hard surface and disguising this with filler can be difficult. Also on long sections pushing out air bubbles is harder.

The instructions suggest cutting edges to shape once located, but you risk tearing the surface and creating rips which are hard to disguise.

After the first day of work, my hands began to feel pretty raw and painful and I found that they were full of tiny spines of fibreglass. I had to soak them in cold water and the discomfort lasted for a few hours. I subsequently used disposable gloves when smoothing out the surfaces.

After painting the surface is sealed but until then I would avoid allowing kids near it (or sliding down the walls in a state of undress!).

I phoned the suppliers to ask if they were aware of this problem and they admitted that they had had previous comments from customers about this. I’m surprised that they don’t warn about this problem. Loft insulation packaging is covered in warnings about fibreglass being an irritant.

ADHESIVE AND FILLER

The adhesive is very expensive and I was annoyed at being recommended one full tub for each roll by the suppliers. I have lots of it left in my shed now despite having used it very liberally as suggested.

I compared it to an old tub of cork tile adhesive and it appears to be the same. Cork adhesive costs considerably less.

The “special” filler seems to be identical to decorators caulk, which I have found for £1.75 a tube, less than half the cost of the Sempatap filler.

I pointed this out to the supplier and they told me that I would invalidate any warranty by using other products (I wasn’t aware that I had one).

DECORATING

The instructions say you can paint straight on to the surface but being fibreglass, it doesn’t take paint well. I had to put on 3 coats before it began to look respectable. It soaks in a lot of paint and you end up with “shiny” areas.

They suggest putting lining paper over joins which I did and again because of the fibreglass surface, the wallpaper glue didn’t adhere well and edges lifted. I used vinyl adhesive to stick down edges in the end.

The contrast in paint finish between the “natural” and lined surface is a bit jarring if you want a uniform paint finish. I got pricey “flat” period paint and it rather negates the effect. I would recommend priming the surface with cheap paint before putting on a special finish.

WHATS IT MADE OF?

I showed it to a friend who works in environmental assessment and he wondered about how sound the production of a new foam material might be.

I have subsequently read about a similar product made from recycled plastics and I will look into this for future insulation of existing solid walls.

COSTS

As well as the costs of the filler and adhesive mentioned before, I found the cost of the actual rolls prohibitive. I benefited form a council discount and a pre-Christmas offer price, but still found an overall cost of over £600 for one floor of a small house to be excessive.

When I did the initial calculations, I would have given up if not for the encouragement of my lodger who is a Sustainability Officer and a staggering gas bill.

LIFESPAN

Already, a few weeks after completing the job, the surface has accumulated snags and tears. I wonder how it would fare in a house with kids on trikes etc. The information gives it a 25-30 year lifespan, but what then?

Having attempted to cut out and replace a section with an annoying air pocket, I can tell you that once set, the adhesive is very strong and you have to scrape it off with a sharp edge.

The sections on the stairs are already scuffed by shoes and fraying.

I can see problems ahead if it is widely used in HMO’s etc.

CONCLUSION

I am pleased with the final results as an insulator, but not so much as a soundproofer, the effects of which incidental rather than real. I wouldn’t have embarked on using a whole roll to limit noise and realise now that I should have used a more specialist product for this.

I have a reasonable level of DIY skills; my father had a small building firm and I have renovated houses and now work in social housing dealing partly with maintenance issues. I have to say that despite this, using Sempatap has been challenging and the whole process has taken a lot longer than anticipated. The leaflet says anyone with reasonable level of DIY skills can use it but I would question what constitutes a reasonable level.

I note that a training course in installation is available for commercial installers, which indicates that a level of specialist skill is required to do a good job.

I wonder if there would be a better take up of this material if an all in supply and installation deal were available.

It is considerably cheaper than exterior insulation for solid walls but I think the costs are still prohibitive.

I would continue to recommend it to anyone considering solid wall insulation but would draw attention to some of the issues listed above.

Mark Mansbridge

26/2/09