Understanding cavity wall insulation

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Chelsea House - London, Prestige Architects By Marco Braghiroli Prestige Architects By Marco Braghiroli Casas de estilo clásico
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Every homeowner hears a lot about cavity wall insulation, but knowing what it is, why it's so essential and how it can benefit a home are essential factors in deciding whether to replace or install it. This guide has been curated to answer any and all questions about the wonder of insulation and it's surprising just how many there actually are. 

While external wall insulation can seem like a far simpler option, cavity wall insulation is where it's at, in terms of modern energy efficiency and it can be shocking how cost-effective it is to install. Breaking down the topic of insulation is more than just vital for effective home ownership, reduced energy bills and building regulation adherence; it's actually quite fascinating as well.

What is it?

 Cavity wall insulation is a form if interior wall insulation and, in basic terms, means installing two structures, with a void between them, which is then filled with an energy efficient material, so as to trap in the heat. In newly-built properties, this is done as standard, during the construction process, but for older homes, retrospective installations can be needed, to improve the heating efficiency. 

Wall insulation panels are a simple way to fit aftermarket cavity insulation in to a home, as they can be fitted as a stud wall, with filling added behind them. There are a number of pros and cons to consider, however:

- Pros:
1. Internal insulation is a far cheaper option that exterior insulation, which is not always an option, as it happens. For homes that are built in a conservation area or have listed status, it might be illegal to change the exterior façade in any way, even in the name of energy efficiency.

- Cons: 

1. It can be considered to be a little less effective than other methods of insulation, as it is thought to be a case of shutting the stable door, after the horse has bolted.

2. It needs to be fitted by qualified professionals, so as to negate potential damp issues.

3. A little internal floor space will have to be sacrificed.

4. The process can be disruptive.

What types are there?

Having made the decision to invest in some cavity wall insulation, there is another pertinent issue facing savvy homeowners; choosing their wall insulation materials. The most common option appears to be wall insulation board, but there are a number of other cavity fillings to become acquainted with.

1. Rigid foam boards.
Though popular, these boards tend to be fairly pricey and won't offer anything in terms of breathability, thanks to being encased in a waterproof membrane  that will protect against damp. Unyielding, the boards are easy to cut with the right blade, but will need to be stored away from the floor.

2. Mineral wools.
Mineral wools are exceptionally popular options and are usually supplied as a quilt-like sheet, making it easy to install and handle.

3. Natural materials.
There are some fantastically organic and eco-friendly options available, meaning that even the most back-to-nature homeowners will be spoilt for choice in terms of insulation options. Popular choices include sheep’s wool, shredded wood pulp and cork. These all offer excellent breathability, can be sourced sustainably and, more importantly, do not release any toxic or semi-toxic gases.

It is also possible to use insulating gels and paints, but this is a little less common and more suited to things like floor voids.

How is it installed?

Installing solid wall insulation isn't as simple as just flinging up a stud wall, which is why a team of professionals will absolutely need to be hired for the task. One thing that does make everything a little simpler, is the fact that regardless of the actual materials being used, the installation process will generally be the same for cavity wall insulation. It should go as follows: 

1. Undertake a proper examination of all internal walls and carry out any necessary repairs.
2. Decide on whether direct wall insulation, insulating with battens or a stud wall design would be best and most beneficial.
3. Make a decision as to the best way to tackle reveals and floor voids. Insulation material manufacturers suggest ideas.
4. Make the walls a blank slate on which to work. This means removing all sockets, woodwork and anything else.
5. Use any necessary primers or preparation solutions.
6. Install the chosen insulation.
7. Seal all the joints, reveals and voids, before applying a skim coat of plaster.
8. Reinstall all wall fixings, including light switches and sockets.

How much does it cost?

A key question when embarking on any dramatic home redesign of development project is how much will it cost to complete and while insulation is most certainly a valuable endeavour, that doesn't mean that the money needed will be pocket change. While free cavity wall insulation can sometimes be available, through an energy efficiency grant, via local councils, internal wall insulation isn't going to be totally free-of-charge for everyone. 

Wall insulation costs generally come in between £40 and £50 per square metre, but this figure can obviously change, according to which materials are being used, but one thing that will always remain static is the percentage of the overall project cost that is attributed to labour. With tis in mind, it can be a little unwise to try and skimp on the thickness of insulation materials, in a bid to cut costs, as the only loser in that situation will be the homeowners themselves.

Why is it so important?

Cavity wall insulation seems to be a time-consuming and, potentially, expensive investment, but it is absolutely worth doing, particularly in older homes that might not be very energy efficient. When it's understood that proper internal insulation can lead to a reduction in household heating bills of almost £500 a year, the facts speak for themselves.

In terms of treating and preventing damp problems, internal insulation is critical, which is another reason why it is considered to be such a valuable investment.

What other benefits does it offer?

Another key consideration is the fact that any homeowner who is looking to sell up at some point will definitely see a better offer price, if internal insulation is in place. With a more impressive Energy Performance Certificate (EPC) on display, homes are far more attractive to potential buyers. The less remedial work that a potential buyer will have to undertake, the better and the higher the selling price of a property should be. 

In essence, internal insulation is something that will pay for itself, either via savings on heating or at the point of sale.

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