Author Archives: James

Thermal Conductivity & U-Values

When you start looking at solid wall insulation as a potential solution for your home or commercial premises, you may come across the terms ‘thermal conductivity’ and ‘U-value’. In this article we are going to try to shed a little light on what they both mean!

Thermal conductivity

Thermal conductivity measures the ease with which heat can travel through a material by conduction, conduction being the main form of heat transfer through insulation. Thermal conductivity is often termed the λ (lambda) value.

The thermal conductivity is a constant for a particular material – it is not impacted by the thickness of the material. Although when comparing different materials, products with lower thermal conductivity values are better insulators (i.e. will be better at slowing heat loss).

At EWI Store we sell three different types of insulation (although there are more types available in the market). The table below shows the different thermal conductivity values for these materials:

Insulation MaterialThermal Conductivity
Expanded Polystyrene (EPS)0.031 W/mK
Extruded Polystyrene (XPS)0.034 W/mK
Rockwool Dual Density Boards0.036 W/mK

So based on the lowest thermal conductivity being the best insulator, from the table above, you can see EPS is the best insulator.

Now – thermal conductivity is useful, but we also need to incorporate the thickness of the insulation into the calculation. The thicker the layer of insulation, the slower the rate of heat loss and also the better at retaining heat a building will be. This is where the U-value comes in. The U-value signifies the heat lost through a given thickness of a particular material. This allows you to directly compare types and thicknesses of insulation.

The calculation is as follows:

U-value = Thermal conductivity / thickness (where the thickness is measured in metres).

When you are comparing U-values, a lower number is better – i.e. a lower U-value signifies less heat loss through a material; therefore it is a better insulator.

U-values and building regulations

Building regulations often provide a U-value number that needs to be achieved when building certain elements of a property. So for example when retrofitting external wall insulation on an old solid wall property, you need to achieve a U-value of 0.3W/m2K or lower. This can be achieved with any insulation material, although the thickness of the particular material will vary; for example when you are using EPS on a solid wall property, 90mm will suffice – but if you were going to use Rockwool, you would require 110mm.

Now, to get a true U-value figure you need to take into account all the different elements that make up the wall: the internal plasterboard, bricks or block work, insulation materials, and even the thin render top coats – they all very slightly change the u-value number.

So there you have it – hopefully that makes understanding U-values and thermal conductivity a little easier! If you would like us to calculate U-values to help you determine the thickness of insulation you require, then please let us know.

Benefits of rendering a building

You might wonder why people to decide to render a property. Well, there are several benefits, which we are going to discuss below.

1 – Protects/weatherproofs your building

The first benefit of render on any building is that it should help weatherproof the underlying brickwork. That means that, regardless of the condition of the existing brick/block work, no water will be able to penetrate through the watertight, weatherproof render finish. We offer 25-year warranties in some cases on our renders, giving you the piece of mind that they are built to last!

2 – Blend new parts of a building to existing

The second benefit of render is that it can be used to blend different types of building together. Say you have an old property built in the 1960s and then decide to get a new extension built on the back of your home. By rendering all the property (old and new), it will tie the look of the house together seamlessly!

3 – Improve the look of the property

Driving around London, the difference between newly rendered properties and older render properties is stark. The older properties look tired and often the render is cracked all over. A new coat of render can really give your property a face lift, making it look like new. Our renders are available in thousands of different colours and lots of different textures so it is easy to achieve the style you are looking for.

4 – Get rid of pebble-dash!

This is a subjective one, but we think pebble-dash looks a bit dated. Our render can go on top of old pebble-dash, giving a much more modern look to these properties! Check out our blog on how to replace pebbledash with coloured render for more info.

5 – New render doesn’t crack

There are lots of different types of render, but the best-known at the moment is probably K-rend. The good news is that some (but not all) modern day renders don’t crack. Take our EWI Pro renders, for example. All of them have a fibreglass mesh base coat layer. This is flexible and moves with the building. The render that sits on top of this base coat layer is extremely thin and flexible. The combination of the two means that our render will not crack!

6 – No need to paint!

All our renders are pre-coloured before delivery (except for mineral render, which comes as a dry mix). The renders are very stable in UV light, meaning that once applied to the wall, the colour will will last 25 years+ without fading.

7 – Modern day renders are cost-effective

Modern day renders are pretty good value – for all the different components combined (basecoat, mesh, primer and render), you are looking at about £10 per m2.

No. 8 – Silicone and Mineral renders are breathable

When you speak to building professionals or architects they will often talk about the breathability of the building. Basically, what this means is that moist air within the building can be dispersed to the external environment, helping to minimise condensation forming inside the property. Condensation can lead to mould and rotting occurring in the building, so obviously if that is minimised it is a good thing!

Our silicone and mineral renders are breathable – this means water vapour can cross through the surface of the silicone, which is a huge benefit to the building.

A happy customer!

It is not often we write blogs like this – normally we are trying to explain a specific feature of the system, or talk about some new product or other – but we thought this story was worth sharing!

Anyway, this morning, Nick was helping a potential installer down on the shop floor. It was a pretty standard chat to be honest, talking about the different system components, training, what other systems the guys had used before, and so forth.

At that moment another one of our new installers came in and said to Nick that our render was the best he had ever used. Now, we don’t know if he was looking for better prices, but talk about perfect timing! I also hasten to add that no brown paper bags were exchanged!

Better than that, it is great to know that the journey we started 3 or 4 years ago launching EWI Pro and EWI Store may work out alright. There is nothing worse than trying to sell a duff product, but the feedback we get from our installer network is that our materials really are second to none.

Also, unlike some of the big boys in the market, we can get materials to you the next day 99% of the time, including coloured renders, which are mixed at our warehouses. We have the capacity to mix 500 buckets of render a day with our colour mixing machines – enough to cover about 5000m2.

We pride ourselves on the quality of products and the great service we provide.

Not too bad! Not too bad at all!

EWI-63331 Bellcast Bead (2m)

Solid wall insulation made easy!

There are lots of components involved when installing solid wall insulation or render systems. What we have done at EWI Store is to try and simply the process for our customers by offering a number of things that our competitors don’t!

1. Use our solid wall insulation calculator.

We have spent the last few months developing a calculator to help users calculate exactly what materials they need for a job. It means that if the size of the area to be rendered or insulated is known then we can automatically provide a shopping list of exactly what is required to do the solid wall insulation install.

The calculator considers the thickness and type of insulation, the adhesives required and even allows you to visualise the colour of the project.

We are very proud of it and you give it a try yourself by clicking external wall insulation materials calculator!

2. Minimising the number of components on site

One of the things we really like about the EWI Pro system aside from the quality of the components is that they have tried to simplify the install process for their installers.

Take for example the adhesives – for many manufacturers they recommend using different adhesives for attaching insulation boards to the wall and then the base coat layer. They have recognised that this can cause issues at the end of job having unused bags, but also the confusion of using the wrong adhesive at the wrong time.

The solution they have come up with is very simple – basically you can use one adhesive (EWI-220) for sticking EPS boards to the wall and then the same adhesive for the base coat layer. Likewise, for Mineral Wool boards they also have manufactured one adhesive that does the job (EWI-225). This means that once you have chosen the insulation material you are going to install on the house, you know that you only need to have one type of adhesive on site. This means no confusion of which to use where, but also it means you shouldn’t have bags left over at the end of the job (and if you do you can take them to the next job knowing you can use them!).

3. We sell all the components for the solid wall insulation/render job

We pride ourselves on the fact we sell all the materials required for the job, so you can complete it from start to finish. We sell everything from starter track up to the verge trim and everything in between. We know how annoying it is when you need to buy a few bits from one supplier and other bits from another.

We also offer all the tools and protective items to get the job done too, just one more reason to shop at EWI Store for you rendering and insulation materials!

baner ewi pro

Welcome to the new EWI Store!

Welcome to our new site – the home of everything to do with solid wall insulation!

At EWI Store we sell award winning solid wall insulation products, all BBA-approved so you can rest assured you are getting the best on the market.

So aside from a new lick of paint, what else is new at EWI Store?

We have a new improved materials calculator – if you haven’t tried it, then you should. It is the perfect way to get the right quantities and proportions of materials. If you are new to solid wall insulation, or EWI Pro specifically, then our tool will ensure you order just right. We have also included our new colour chart in the latest iteration to allow you to see a little more accurately what your property may look like once the insulation is installed.

While we are talking about the colour chart, we now offer a standalone colour chart tool to allow you to quick and easily pick the colour you want. We have cut down the number of stock colours we offer, instead we are focusing just on the most popular renders we have sold over the last 3 years. The reason for this is pretty simple: too much choice seems to be a bad thing!

Happy render, happy customers…

Installers are telling us that providing customers with so much choice just delays decisions. Choosing between 3 near-identical grey colours appears to take some weeks it seems and therefore we have reduced the choice to help speed things up a little! We also have a new pricing system for our colours. The white colour has no additional charge, off whites (known as Tier 1 colours) are £4 per bucket, Tier 2 colours are £12 per bucket (these tend to be slightly darker colours) and Tier 3 (really vibrant/dark colours) are £20 per bucket. Obviously if you are a trade customer, trade discounts apply. If you desperately need a colour not included on our minimised colour chart then we can obviously make these; however additional charges may apply!

We are also delighted to now offer verge trims. These are the aluminium bits that go on the top of the solid wall insulation system; they are used to help prevent water ingress down the back of the system. These are all made in the UK and although we have standard profiles, these can be adjusted if required to suit the needs of the installer.

The good news is that despite the new shiny website, it is business as usual here at EWI Store, so if you need a great value solid wall insulation system with unparalleled support (and free training!) then get in touch. You might even want to give our EWI materials a calculator a try to get started….

Go on – give it a try!

James

buy renders and EWI Systems from EWI Store

EWI – wet fix versus dry fix systems

When solid wall insulation is installed on brick or block work, it is very important the insulation material used stays in place. This goes with out saying to be honest: the reason being if the insulation were to move once installed, the whole of the system would come away from the wall – not ideal!

There are three different ways to attach the insulation boards to the wall:

  1. Attach with an adhesive (wet system)
  2. Attach with mechanical fixings (dry system)
  3. A combination of 1 & 2 (the best system!)

At EWI Store, we offer the BBA-approved EWI Pro external wall insulation system. This system is great for improving the thermal comfort of your home, lowering energy bills and also giving your property a complete facelift. It is also a belt-and-braces system: that is, it uses a combination of both adhesive and mechanical fixings.

You might ask why we bother – there is certainly more work if you are sticking the boards to the wall first with adhesive and then using supplementary mechanical fixings.

There are several reasons why we recommend a wet fix system with supplementary mechanical fixings

1. We want to sell solid wall insulation that lasts!

If you use only adhesive or mechanical fixings then the insulation boards are never held in place as firmly as when you use a combination of the two. We want to sell systems that are going to last many decades once installed, so we always advise to use both adhesive and mechanical fixings.

2. Dry fix only systems can suffer from draughts!

If you use dry fix systems then cold draughts can travel up the back of the boards, limiting the impact of the insulation. The cold draughts can accelerate the rate of heat loss, but if the winds are strong enough they can also try and pull the insulation from the wall.

Using the envelope method to apply the adhesive on each board means no draughts can travel behind the boards. This limits heat loss and ensures that the boards are held firmly in place.

3. Adhesive acts as a leveller!

The great thing about the UK is that we have some of the most diverse building stock in the whole world. Historically, we have made houses that are going to last – which is great – but it is fair to say that building methods from yesteryear didn’t always result in a straight wall!

By using adhesive on the back of the insulation boards, you can help level out some of the discrepancies in the wall. Obviously it is not going to be possible every time if the wall is really wonky, but it should certainly help take out some of the kinks!

We often refer to the EWI Pro external wall insulation as a belt-and-braces system: i.e. you are going above and beyond what is potentially required. But if you want these systems to last then we certainly recommend it is worth doing!

The Advantages of Rockwool Insulation

We are delighted to be able to offer Rockwool insulation as part of our external wall insulation systems. Rockwool are currently the world leaders in the manufacture of mineral wool insulation, manufacturing their stone wool from a blend of naturally-occurring volcanic diabase rock. This rock is heated to an incredibly high temperature and spun (much like candy floss) into a fine wool that then can be used as an insulation material for many different purposes.

Rockwool historically have made rolls of loft insulation and cavity batons; however the insulation we sell is specifically made for solid wall insulation.

The stone wool is compressed into dual density rigid boards. The outer most surface of the insulation board is compressed to a higher degree than the rest of the board. This means the surface is that bit stronger and therefore it provides more compressive strength when used in the insulation system.

The Advantages of Rockwool

Rockwool has some significant advantages over other insulation materials which are discussed briefly below:

  • Rockwool stone wool fibres can withstand more than 1000°C without melting – this means it can slow the spread of fire in a property where it to catch fire.
  • Rockwool has fantastic thermal insulating properties. 120mm of our dual density slabs when attached to the exterior of a property will take the u-value down to 0.3 which means the building will then conform to building regulations. For the occupants, it means improved thermal comfort since the property will stay at more even temperatures and also lower energy bills.
  • Rockwool stone wool has great acoustic insulating properties, so it can really can help with sound reduction if installed on a busy road for example.
  • The final advantage is that Rockwool is breathable, therefore it allows moisture to travel across the wall which can help dissipate damp (from in the house).

In order to use Rockwool stone wool in our external wall insulation systems, you do need to use slightly different materials, because the adhesive required to stick the boards on to the wall needs to be slightly stronger. Since the Rockwool is also breathable, we don’t sell acrylic render for use on this system as it slightly defeats the object!

Looking for a Quote for Rockwool? Try our calculator tool!

How to Install a Rockwool EWI System

When installing Rockwool as part of a Mineral Wool external wall insulation system, we recommend the use of our Premium Adhesive. This is our strongest and most breathable adhesive; it contains strands of fibreglass within the material, which enhances its tensile strength and adhesive capabilities. The Premium Adhesive is used to secure the Mineral Wool boards to the substrate, before metal mechanical fixings are drilled in to provide an extra secure fit. Metal fixings must be used in conjunction with Rockwool because this is a much heavier insulation material and plastic fixings wouldn’t be able to take the weight of the boards.

From then on, the Premium Adhesive can be used on top of the boards as a basecoat, with strips of overlapping fibreglass mesh embedded within it, before it is finished with either our Silicone or Silicone Silicate renders. We advise using these renders as they are our most breathable and therefore will work well in conjunction with the Rockwool which is, as stated above, a highly breathable insulation material.

Looking for a comparison between all three of our insulation materials? Have a read of our blog post ‘the best insulation material for EWI?’. We’ve also previously written all about our Wood Fibre insulation and the advantages of that on another blog post, so have a read before making a decision!

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