Tag Archives: Passivhaus

building regulations and U-values, EWI, external wall insulation and U values

External Insulation for Passive Houses?

What is a Passive House?

Passive Houses and external wall insulation are two hot topics within the energy efficiency and insulation industries. Passive House is a construction concept that originally began in Germany; initially coined ‘passivhaus,’ it is generally known as an energy efficient, environmentally friendly house that practically requires no heating. The building is constructed in such a way that it is tightly sealed in a thermal envelope which allows very little heat to escape, so that essentially a room can be warmed simply by light from the sun, body heat or the heat from small electrical appliances. 

There are three things that a house needs to achieve before it can be considered a Passive House:

  • A Passive House needs to have primary energy demands (such as warm water, heating, house appliances) lower than 120 kWh/m2a
  • A Passive House needs to have heating demands lower than 15 kWh per square meter annually.
  • A Passive House must pass a pressure test and the pressure must be limited to 50 Pascals with the pressure differential not exceeding 0.6 times a room’s volume per hour.

A Passive House has a high level of insulation. That includes the doors, windows (triple glazed), walls, floors and roof. However, as we know, houses need proper ventilation – therefore Passive Houses also require a mechanical ventilation system.

Excellent indoor air quality is a characteristic that Passive Houses possess, and this is achieved through the mechanical ventilator exchanging the air from inside with the air from outside. These are great for being energy efficient, because during the process of heat exchange the ventilators can transfer the fresh air into the room at the same time as heating up/cooling down the fresh air. This means that Passive Houses are able to exist without the frequent or constant use of conventional heating systems, many only have one radiator in the bathroom for drying off towels.

External Wall Insulation on Passive Houses

So, as previously mentioned, Passive Houses require an outstanding amount of insulation; typically a Passive House wall will have a U-value of 0.15m/m2k. Luckily, external wall insulation would do the job perfectly if you get it at the right thickness. EPS, Mineral Wool and Wood Fibre have low enough U-values to be able to obtain the required level of insulation for a passive house.

However, the insulation needs to be totally sealed against thermal bridging– which means absolutely no gaps. This is because gaps in the insulation break the thermal envelope and, especially in highly insulated houses, reduce the effectiveness of the insulation. Thermal Bridging can cause damp and condensation – which can be far more detrimental to a passive house than a regular house.

Which EWI System is Best for a Passive House?

To achieve Passive House U-values on a 215mm solid brick wall, 270mm of Mineral Wool would be required. Mineral Wool is highly breathable so it’s great for a Passive House construction where ventilation and air quality are key in order to prevent damp. Due to the fact that Mineral Wool is made of a renewable material (volcanic rock), it’s also in keeping with the ethos of the Passive House. Rockwool is made by spinning volcanic rock in a furnace at a high temperature to create a cotton candy-like texture, and then it’s compressed into dense, flat insulation boards. Rock is not a very good heat conductor, and the fibres from the spun rock provide air pockets, which is what makes it a great insulation material.

In keeping with the Passive House rules, the EWI-225 Premium Adhesive, designed for use in Rockwool systems, is also ideal because it is breathable, strong and waterproof.

To finish off the system, for a Passive House you will want to use a Silicone Render. Again, this works really well in conjunction with the Rockwool system because of its breathability. Silicone Render is hydrophobic (water repelling) so moisture will essentially bounce off its surface, safeguarding the system against damp.

Wood Fibre Insulation for Passive Houses

Our most environmentally friendly insulation material is our Wood Fibre insulation, which we source from Pavatex. To achieve Passive House U-values with Wood Fibre on a 215mm solid brick wall, you would need 240mm of insulation. Wood Fibre is a highly versatile insulation material, offering excellent thermal performance. Our Wood Fibre insulation is completely recyclable and holds the prestigious title of being NaturePlus certified. The fact that this insulation is so highly renewable and environmentally friendly means that really it’s ideal for Passive Houses where environmental consciousness is at the forefront of the building design. Passive Houses also require a high level of breathability, and Wood Fibre is the most recommended insulation material to achieve this.

Building a Passive House is a highly technical procedure, and external wall insulation could definitely play a part in helping to mimic the Passive House standards. Our sales team are experts on all of our products and will be able to give you any technical advice about their technical specifications and usage. Feel free to contact us for any questions regarding our materials or get yourself a free materials quote using our calculator!

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Why is EWI the Future?

The market for external wall insulation in the UK has rapidly expanded over the last few years, with more and more homeowners becoming aware of the process as a solution to energy efficiency. There are some out there who are skeptical about the future for external wall insulation, with negative doubts towards the technology and the reliability of retrofitting.

In this blog post we thought we would talk a little bit about why we think that external wall insulation has a long future ahead!

New Build Properties

These days, more and more people are worrying about the pros and cons of investing in new builds. The UK housing stock is rapidly growing, and the quality of newly built houses are under scrutiny from potential buyers and the media. While today’s new builds must achieve the regulatory U-values for a property, some homeowners are reluctant to invest in newly built homes due to concerns surrounding the quality of build, static resale values for at least five years and premium prices.

The appeal of investing in a quality older property, and instead spending the money on doing it up and improving its energy efficiency in other ways (and consequently improving its value) is an appealing choice for many homeowners. Among one of these methods of improvement is external wall insulation.

Growing Interest in Passivhaus Standards

EWI can contribute to passivhaus standards which is becoming a new trend for building design. Awareness of the passivhaus building style is gradually growing within the UK, with environmentally aware homeowners becoming more and more intrigued about how this level of insulation might be mimicked.

Enter external wall insulation – a way of improving the energy efficiency standards of a property by simply retrofitting it to the existing building. EWI may not make your home a Passivhaus, but it can certainly work wonders on dramatically improving your U-values and energy output.  

Large Quantities of Solid Wall Properties

To this day there are approximately 9 million solid wall properties in the UK. This means that 9 million homes do not have adequate insulation and are therefore functioning inefficiently.  External wall insulation is the best solution in these circumstances, since internal wall insulation simply doesn’t have the same high performance results.

Rising Energy Prices

Energy prices go up by around 5% each year. As household bills become more expensive, heating the home with traditional heating methods will become more and more costly. People are therefore better off focussing on effective insulation to combat the need to excessively heat the home and rack up the pricey energy bills.

Growing Technology

Because external wall insulation is a growing construction process, the current technology is extremely up to date and is only getting more advanced. The effectiveness of the system will only keep improving and here at EWI store we hope to keep growing with it. Take for example the groundbreaking thin coat render systems, including silicone render technologies that provide unbeatable hydrophobic properties.   

EWI is also growing in a appeal to those who may not have ever considered anything of the sort – at the beginning, there were worries that the EWI would ruin the external walls of the property, when in actual fact it protects them against weathering. There has also been advances in research about different substrates and the best materials for them. For example timber frame properties need to breathe, therefore breathable materials (e.g. wood fibre insulation) are really on the rise.

The continued visual and aesthetic appeal of EWI is also of interest to homeowners. There are now many cases where EWI has vastly improved the look of the property and the technology behind this is continuously developing. Take for example our Acrylic brick slips and our wood effect render. The wood effect render is actually a really clever way of mimicking timber beams without the hazard of the wood rotting or posing a fire risk.

UK Housing Situation

As the UK housing crisis continues, people are more concerned about investing in the longevity of their homes – ensuring that they last and that they are saleable. Investing in EWI is a great way to extend the life of a property because, as previously mentioned, it protects the external walls of the property. It can also improve the value of the property due to higher EPC ratings, lower U-values, lower energy bills and increased visual appeal.

Increased Awareness of Climate Change

The media and the government are currently paying a lot of attention to climate change and how we can combat this. As a result, there has been a huge surge in people who are keen on making a difference in combating climate change and saving energy. This is encouraging growth in interest in energy saving from an environmental perspective as well as money-saving. Homeowners are keen on external wall insulation because with EWI the need to heat their homes is decreased dramatically, thereby reducing their carbon footprints.

Changing Energy Efficiency Standards

Required energy efficiency standards are going to get a lot tighter as climate change continues. 2018 has brought the landlords minimum energy efficiency standards (MEES) regulations. The main aim of the MEES is to prevent fuel poverty by ensuring that rental properties have an EPC rating at a minimum of E.

This is the first in energy efficiency regulations and we hope that more regulations such as these will be brought forward to help cut down on inefficient energy usage.

Growing Awareness

Excitingly, general awareness of external wall insulation is growing, and as a result more and more installers are offering external wall insulation install jobs. Installing EWI is a complicated procedure and needs to be done properly. We recommend that you always choose trustworthy installers to carry it out, and we have a database of trusted installers all over the country who we can point you in the direction of. So get in touch and we can pass you on!

Stay tuned for more blog content! We upload every Tuesday and Thursday all about our EWI and render systems, answering FAQ’s and giving full and detailed product guides.

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