Maintenance and the consumer society

One might think that with the growth of consumerism that we would naturally consume more maintenance products for our homes, but the trend seems to be the opposite.

The rush to be at the front of the queue for the latest gadgets etc does not sit well with the need for the regular and mundane nature of building maintenance. Checking whether you have cracked render, failed silicon around the windows, leaking gutters etc is not as glamorous as a new internet accessing tool.

So I often find that some houses with easily fixable problems (like many damp issues) get to the state where a 'damp proof expert' ends up recommending an expensive (and completely inappropriate) solution. These homes are often stuffed to the gunnels with disposable electronic kit, so there is not a lack of money, just a lack of priorities.

The 'quick fix' nature associated with modern consumerism doesn't help here either. Once people see that they have a problem any solution must be quick, cheap, no hassle, immediate, ... Unfortunately, due to the delay in acting they have often missed the boat. If maintenance is done regularly then you can use quick fix solutions. For example:

If you see that your silicon has failed around the windows, then it is a quick job to remove the old and replace with new. This will stop any more water getting into the structure. Simple. However, because people don't do this, the first they will know will be when damp has penetrated through the structure and the plaster inside has failed. This then becomes a job that might involve replastering, redecorating etc.

Exmaple #2: If you see that the ventilation grills on your ground floor are becoming blocked, just clean them up. Simple. If you don't then your solum (underfloor area between the wooden floor and the earth) won't work properly and eventually the floor joists will start to rot etc. This then becomes a major job. It will also take a nasty turn, as the builder coming in will fill your mind with having the floor replaced with a concrete one. This will of course be maintenance free!!! Naturally the new concrete floor with cause a range of new damp problems, ..........

So take a break from the computer / curved screen TV / smarter (than 6 months ago) phone and get outside and have a look at your biggest ever investment and give it a few precious minutes of your time. This will save you a lot of heartbreak, money and time resources in the long term. A few basic tools will allow you to do most of the work yourself (or it will be cheap for a good handyperson to fix for you). Houses are not as addictive as modern consumerist stuff, but they can a real drain on your resources if you ignore them for too long.

I would recommend checking the following:

Windows and door seals (esp. those facing the prevailing winds)

Guttering

Renders / pointing (again esp. those facing the wind and rain)

Drains around the house (to ensure that water is being taken away from the walls)

The roof (to spot any broken or slipped tiles)

Vents and extracts (clear to ensure that they are working properly)

I reckon that a thorough check will take around 5 or 10 mins. 

Then it is a case of keeping your eyes, nose and ears open for any changes. A new drip might be the first sign of a guttering issue. A small damp patch might indicate the need for a check of the seals around the window. A musty smell might alert you to a blocked vent, ....

So when you look at it this way, actually you can fit in all the consumerist stuff that you like and some basic checks on your home. For more guidance on maintenance, especially on older properties have a look at Cadw's Maintenance Matters website.

What constitutes a 'healthy' home?

Health is really important to all of us, yet many of us live in houses with poor internal environments. Some of this is our own fault - we clean using dangerous chemicals; we allow properties to get into a poor state and hence introduce damp from rain; we don't ventilate properly; etc. However, some of it down to the structure of the building. So I thought that it might be worth investigating the idea that using health as opposed to pure energy efficiency could be a way forward for improvements in the housing sector.

So what are the key health factors that could be used to drive new specifications for home improvements?

Allergies

People seem to be getting more sensitive to substances, many of which are airborne. So there is a need for better Internal Air Quality (IAQ) in our homes. Having filters in ventilation systems is an obvious way of improving the situation for cleaning any air coming into our homes, however most properties do not have whole house ventilation systems, but there is a trend towards positive pressure ventilation in retrofits. These units can have filters fitted, but it does mean that they have to be cleaned / maintained on a regular basis and so this means that we have to have a system in place to ensure that this actually happens (otherwise it is waste of money and resources).

Many materials continue to off gas substances throughout their lives, so it usually better to use natural materials that have been treated with natural preservatives / protecting coats.

The main source of allergies, though comes through from our foods and the effects of our lifestyle choices. This could be the type of cleaning materials that we use, whether we smoke in the house etc.

However we can reduce dust circulation by using radiant wall heating rather than conventional radiators or underfloor heating.

Respiratory diseases

Respiratory problems are caused by a range of root causes many of which can be tackled during refurbishment. Issues like high / low humidity, mould and dust can all be effected by what we do to our homes.

It is really important that we manage ventilation in our homes as this helps to control humidity, but it is equally important that we allow any breathing walls to continue to do so. Sealing up older 'moist' walls can introduce damp and hence mould etc. Having a relative humidity of between 50 and 60 per cent minimises the risks associated with dust mites etc and this range can be maintained by the use breathable solid walls. We must also be careful when installing insulation, as poor fitting / specification can introduce cold spots and this in turn can easily create damp / mould issues.

Automatic ventilation control systems that run off information like relative humidity and CO2 levels can really assist with maintaining a good internal air quality. These can be installed where there is a good airtightness in the building and ideally systems would also have heat recovery built in.

Temperature related troubles

Overheating and underheating can cause or exacerbate serious medical conditions, so again we must ensure that properties do not get too hot, or too cold. So design is really important to make sure that properties can cope with the projected changes in climate which suggest that our weather will get more extreme in the future, especially with hot conditions. Unless of course the Atlantic Conveyor gives in and we might then become much, much colder in the winter.

So must ensure that properties are designed for both. Using high thermal capacity insulations like woodfibre boards and batts can assist with this. Being able to create homes that can easily and cheaply maintain a comfortable 19 degrees C in both summer and winter is important.

Highly efficient heating systems need to be used that are appropriate for the type of house, so care is required to specify the best type of system. Some houses only served by oil and electricity, others gas etc, so the most efficient systems need to be specified and this might involve additional works. For example ground source heat pumps (GSHP) only work well at low temperatures and so a well insulated house with managed ventilation is required here. A very efficient GSHP in a poorly insulated and draughty home will be very inefficient.

Mental health

Now this is a real bag of worms. Issues like stress can come from a wide range of factors that can be designed out (or into) our buildings. Common factors that effect stress at home include:

Money worries - making our homes cheap to run is really important (as long as we don't cause lots of 'unintended consequences' at the same time). So installing systems that improve energy efficiency, reduce water consumption, minimise maintenance costs, prolong maintenance intervals etc. is really important. Renewable energy systems that attract support can also help to relieve financial pressures by providing some free energy, but also a small income. However, it should be remembered that people make choices when it comes to spending their money and it may be that the best ones are not always taken.

Families - families don't always get along and having separate spaces can be useful. Knocking through reception rooms to make large spaces may not be the best solution. Sound proofing between rooms is also important to create more private space. Having bedrooms that are acoustically isolated can make sleep better and this can be really important.

Neighbours - again neighbours can be a source of comfort or stress. Whichever it is, having good acoustic barriers between the two houses is important. It is also important that any thermal improvements to one house do not cause problems with any adjoining property. So care needs to be taken here.

Natural light - a lack of natural light effects many people, especially those suffering from SAD and so it is important to ensure that light is maximised. This might mean using sun tubes, roof windows etc.

Worries about safety and security - using good quality doors, windows and fixings, combined with clever design can create homes that both feel, and are, more secure. 

Alleviation of niggles - of course there are no end of these, but some are avoidable: Alleviating pressure drops in hot water when more than two outlets are being used; use of long life bulbs to reduce need for replacement; easy access to water stop-cocks if there is a major leak; isolation valves on water outlets for easy routine maintenance; use of siphon toilets rather than valve to stop constant leaks; use of metal rainwater goods to reduce water damage from leaking or damaged plastic ones; use of breathable paints on breathable walls to reduce re-painting requirements; no drylining allowed to reduce issues associated with just hiding problems etc etc.

Conclusion

When we start to think about our homes in more detail one realises that we need homes that feature:

• Good, well controlled, ventilation (e.g using CO2 and RH controls)
• Appropriately insulated both against heat loss but also heat gain (e.g  use of wood fibre insulation)
• Minimised the use of water (e.g pulse shower heads, variable siphon flushes etc.)
• Take advantage of any appropriate renewable energy generation potential (e.g FiT and RHI measures)
• Minimised use of energy (e.g LED lights)
• Have good acoustic insulation both between houses and within them (especially bedrooms)
• Have a mix of private and public space 
• Have sufficient natural light (e.g using sun tubes etc.)
• Are free from risk of damp and mould (using correct breathable materials)
• Use natural materials that are less likely to off gas toxic substances (e.g wood)
• Use materials cleverly to minimise maintenance requirements (check compatibility of materials)
• Use good quality materials that provide long term solutions to safety and security (good quality doors, windows and locks)

Now all of that is a tad more involved than indiscriminately slapping on EPS external wall insulation and changing a boiler, however if we start to think more about maintaining a good, healthy internal environment then maybe we can reduce costs on the health service as well as providing better housing for the great British public.

The British Thoractic Society estimates overall costs to the country of £6.6 billion due to respiratory disease (or which Gov. says £1 billion is spent annually by the NHS on chronic obstructive Pulmonary Diseases)

The NHS has figures of around 31,000 cold related deaths in 2012-13.

The NHS also has a plan in place for heat related illnesses. (pdf format)

The NHS also spends around £16 billion on stress and anxiety related illnesses annually (pdf file).

So improving our homes will not eradicate these costs, but it will have some effect. So we can either look to continue doing 'improvements' that only tackle a small fraction of the issues facing our stock (and even this we are doing badly in many cases - and this causes more stress and more long term financial costs to the country) or we can start to create a nation of healthy homes.

Let's reveal the importance of reveals

Barry Turner's picture shows how IWI is commonly fitted

There will be some research coming out soon that starts to explore the importance on the detailing aspect of insulation works.

The work has focused on the issues of thermal bridges around windows and doors. These thermal bridges (cold spots) that are created by the fact that many insulation systems do not insulate around doors and windows (the reveals). The norm for most insulation works is to stick on lots of insulation to the main walls, but the more complicated and difficult reveals are just left devoid of any insulation.

The effects of missing this insulation vary between properties because houses have different types of wall, different sized windows and doors, different orientations, ... However, it is possible to model the thermal performance of the house to see what effects are likely. Bearing in mind that 'all models are wrong, but some are useful' one cannot predict exactly how any one situation will play out in real life but there are some useful pointers that come out of the work.

One of the worked examples shows that by applying 100mm of insulation to the walls only is actually less energy efficient that applying 20mm of insulation to all the surfaces (i.e. including the reveals).

The trouble is that you generally need a thin insulation around windows so that the operation of the windows and doors are not impeded. The main insulation companies use cheap EPS insulation systems and these boards are too thick for use around reveals. So they don't. If you wanted to use a thin insulation material like aerogel then this would be deemed to be incompatible with the main system and hence would invalidate any warranty offered. So people are left with having the choice between a warrantied insulation system that won't work as well as predicted and might actually cause some 'unintended consequences' (resultant cold spots can attract condensation and mould) and a system that would probably be much more efficient, but would not be guaranteed. Unfortunately we tend to err on the side of caution when we have such major refurbishments undertaken. Of course only time will tell if the warranties that companies offer are actually worth their salt. One imagines that they will be toothless and won't be worth the paper that they are written on, but we shall see.

The issues of reveal insulation are applicable both for IWI and EWI (Internal and External Wall Insulation), but the timescales, knowledge and budgets associated with the most of this work will mean that an opportunity for better improvements will be lost. What makes it worse is that already companies are having to go back to the work that they did a couple of years ago and un-do much of it. This is a shocking waste of money, resources, carbon as well as a double dose of disruption for the householder. 

Work for groups like the Passive House Trust and others seems to be highlighting that actually doing thermal improvements properly would save more carbon than the mass roll-outs are actually producing. There is a cost issue associated with this as each property would be more expensive to insulate (due to more expensive materials being used and the time required for the detailing). The idea of doing fewer buildings properly is not as attractive to politicians as mass roll outs to the fuel poor, even if the carbon savings would be greater.

The trouble with the decision making system in the UK is that it is driven by the tools that are available to it. The use of things like Energy Performance Certificates and the spreadsheet assumptions that underpin it mean that reveal detailing is not taken into account. Moisture and condensation risks are also not part of the calculations. So the extrapolated predictions that are created by EPCs are fundamentally wrong and misleading, but it is all that councils, Government and Housing Associations have to go on. So no wonder we continue to store up problems in our housing stock. I feel a hobby horse coming along!!

Breathe....

The importance of reducing thermal bridging is really important in terms of energy efficiency and carbon reduction, so if you have any control over the process at all we would recommend ensuring that insulation in the reveals is specified and installed correctly. Easier said than done, but getting insulation right is possible, it's just that you need to be aware of the 'pinch points'.

Ventilation vs Energy Efficiency

Ventilation does not mean uncontrolled draughts!

Ventilation is key for all buildings, after all we do need a bit of the fresh air stuff to stay alive! However for older buildings it is even more important. Solid walled buildings should be regarded as having 'moist' walls and hence they dry to the inside as well as the out (assuming that they have not been covered with cement render!) They therefore allow moisture into the internal environment and this needs to be wicked away along with all the moisture that we bring into our homes.

To illustrate this one study found that in a house we produce the following daily:

1.25 litres per person (just by breathing and sweating)

2.40 litres by showering, bathing etc

1.75 litres from a gas oven

1.00 litres from plants (assuming 25-30 plants per house)

....

So we are looking at around 10 litres of water per day from a family of four. All this water needs to be removed from the house and this requires ventilation.

Understanding how this works is really important, but actually very difficult. Where does the fresh air come from? Draughts around doors and windows? Chimneys? Punctures through the walls that have been poorly sealed? Where does it leave the house? Mechanical extracts? Chimneys? Trickle vents? Windows? Lofts?

Housing Associations and others are now wising up to the need for ventilation (after all many of their complaints are about damp and mould). Most are now fitting 2 x low energy vents in houses that run constantly. These only cost around £5 a year to run and can help tremendously with ventilation, but still people will turn them off! This is because people associate ventilation with increased energy consumption and hence costs.

Energy efficiency though is affected by poor ventilation. If walls are wet due to poor ventilation then the walls will be less efficient (by a factor of around 30%). So actually having good ventilation can help with energy efficiency. However most importantly ventilation is important for the health of the occupants and the health of the building itself. Without ventilation we are more likely to end up with mould and damp issues and this then leads to additional expense dealing with this. So it is a false economy in not venting well.

Ventilation is therefore linked to energy efficiency in several ways
So how to go about this?

Well there is no easy answer as each house is different (construction, levels of moisture, knowledge of occupants, lifestyles etc etc). So the best way is to use tools that measure what is actually happening and then automatically adjust ventilation rates.

Modern systems monitor and control a range of factors like temperature, humidity and CO2

These systems are not cheap and generally require a whole house solution with heat recovery (MVHR). These systems require vents to be placed in each room for either extract or input (or both). These are then combined (via ventilation ducts) in a central unit where the outgoing warm moist air help to pre-warm the incoming fresh air. These systems can work really well, but they need the house to be well sealed before they are fitted. They also require the ducts to be passed through the house etc. So these are quite complicated systems, but certainly the most effective as they help save the warm air in the house and therefore are more energy efficient.

Older houses of course are more difficult as they are harder to make airtight. However due to improvements over time many of these houses are now lacking in ventilation. People have fitted doubled glazed windows and doors (many of which have not had trickle vents specified), chimneys have been blocked up, suspended floors have been replaced with solid, lofts have been insulated, hatches draught proofed etc.

This has meant that whilst many houses do not have the required airtightness for efficient MVHR they are lacking in the required background ventilation to remove the 10 litres of water a day needed. Rock and a hard place territory!

So the exercise becomes a little vague and distinctly difficult, especially where people are not used to having (or paying for) pressure tests on their homes. So we are in the territory of 'guestimating'. This is not ideal, but it is really poorly understood area of housing. So you may well find that you are the best person to make decisions on this, after all you will know how bad issues like condensation, mould and stale air are in the house and whereabouts it occurs most and when. So spend a little time thinking about where any problems are and what the root cause may be.

Windows and trickle vents
Chimneys and vents
Draught proofing measures
Extract fans and their direction of venting
Floor ventilation
Airflow in and between rooms (is furniture hard against walls? Is there an airgap at the top or bottom of internal doors? Are certain areas sealed off from the rest of the building?)
Functions of rooms (bedrooms, kitchens and bathrooms are subject to high humidity)
Thermal bridging / cold spots (these attract condensation)

Uncontrolled ventilation via major draughts around doors and windows, floors etc is not the answer though. This can be a real drain on resources as you cannot adjust the airflow to meet the ventilation needs of the building, so make sure that any major draughts are dealt with properly, but be aware that by reducing the uncontrolled airflow that you should be thinking about installing controllable airflow. For example, if you are replacing some old draughty windows then replace them with well sealed units that have adjustable trickle vents on.

Many social housing providers now also fit Positive Input Ventilation systems to reduce humidity levels in their houses. These systems can be simple and easy to install in houses with lofts. Basically they pump air from the loft into the house constantly and the warm moist air is pushed out of the various holes in the housing envelope. They have had a variety of reviews, but those houses that suffer most from high humidity / condensation issues seem to see the best results. I may well try a system in my house and then I can speak with a bit more authority!

Personally I think that buildings need to have:

- extracts in the main moisture generating areas, i.e. kitchen and bathrooms (these should be through walls that are not subjected to the prevailing winds and where this is necessary they should have vent covers installed).
- background trickle vents in windows
- where no trickle vents then 2 x background vents should be installed, ideally these will be heat recovery units that can exchange warmth from the stale air and impart it to the incoming fresh air
- all chimneys should be vented (both at the top and at each breast)
- ideally the whole wall structure should still be breathable
- suspended floors should be vented correctly
- all loft space should be vented correctly
- potentially a Positive Ventilation System installed

This should be treated as guidance to minimise the risks associated with poor ventilation. Most importantly remember that ventilation is not an 'enemy' of energy efficiency. It is a requirement of a healthy house.

Windows shrink with age

Having knocked off most of the render around my house (we are leaving those walls that will not benefit from a new lime render) the original reveals for the windows and doors are fully exposed. This then gives one a chance to see how big the original frames would have been.

One downstairs window has a gap of 3 inches / 75mm each side, so over time my window has effectively been shrunk by 6 inches / 150mm. That's quite a lot of light that I have lost!

What happens is that when windows are replaced we don't hack off the render or plaster to see where the structure is. The windows are measured using the visible reveal. No installer wants to estimate depths that they cannot see and most people don't want to have their reveals knocked around just to get an accurate measurement. So windows get smaller.

When the windows are installed, they do have to 'mess' with the reveal and then you find out that you could have had a larger window, but by then it is too late. The new windows are fitted and the reveals are extended so that the window frame is enclosed with plaster etc. Next time, of course, your reveal is now smaller and the process repeats itself.

I would estimate that around 0.5 - 0.75 inches (12 - 18mm) is lost per fitting, so this would mean that this window has been replaced about 5 times since construction.

One of the other common occurrences with this process is that this gap is often filled with that days newspaper. So, you can often catch up on the news from a couple of decades ago! Nowadays fitters tend to use expanding foam to seal up these gaping holes around your windows which is not so much fun. I am not a fan of this foam and so I have used some fluffy insulation in the gaps to provide a little more warmth (and more importantly) fewer thermal bridges around the edge of the window.

So, if you want to keep your windows as big as possible, you will need to allow fitters to remove the plaster around the window so that they can accurately measure the size of the original window void. This is unsightly and dusty, but it is the only way that a company can reliably measure up. They are not keen on making windows too large or tight as it means that they are responsible for getting it right, so their eye on caution is understandable given the costs of re-making the frames and glazing.

Bay windows

Many older properties have attractive bay windows. However there is an issue that tends to go un-noticed by the great buying public. That of insulation in the bay. Basically there isn't any. The mullions and walls under the window are generally solid walls. This is not too much of an issue as the rest of the house will tend to be the same. However, insulating them is an issue to get right. However, this is the smallest problem. The main issue is that of the roof above the bay.

They tend to look a bit like this:

So there is virtually nothing between you and the outside world. A piece of plaster board / lath and plaster and then a void and the bay roof. So these structures are very draughty and not very insulating. So if improving an older property with a bay, this is one of the first things that needs to the addressed.

It is an easy (if disruptive) fix, as the installation of insulation is relatively simple and then it is a case of just making sure that the details are right. This basically means that you have to get the airtightness correct, so use good quality tapes and sealants to ensure that the final finish is well draught proofed.

Note that this situation can be mirrored under the bay if it is an 'unsupported' bay. These types of bays tend to be seen on more modern buildings and / or on replaced bays as they are cheaper. However, they are rarely sealed correctly and hence tend to be very draughty and again poorly insulated. Thankfully they also tend to be timber framed and hence are relatively easy to improve by using conventional insulation, membranes and good tapes.

If you are installing external wall insulation remember that the wall behind the bay also needs to be insulated to stop thermal bridging. Where the roof is tied into the wall will create a thermal bridge as well so think about how this will be dealt with.

Ultra Insulating Windows and Doors

Eco Home Centre has a great relationship with ARU Joinery in Estonia. Now the lovely people at ARU have developed a brand new ultra insulating range of doors and windows for the Passive House / Code for Sustainable Homes Level 5 and 6 market.

The Nordic Range is made from solid wood so there is no chance of the frames de-laminating. (De-lamination has been a cause for concern on insulated windows and doors as there is an inherent weak point in the structure.) These frames are chunky at 92mm thick, but this is required to house the 52mm deep triple glazed units. The frames, though, do not look over heavy (despite being very heavy!)

The U values achieved are very impressive. The glazing itself gives a Ug of 0.47 and a standard window gives an overall Uw of 0.78. Compare this to the Building Regulations standard of around Uw of 2 and we start to see how well these windows and doors perform.

The Nordic series of products is wide ranging and includes:

• Inward and outward opening doors and windows;
• Sliding patio doors; and
• Folding patio doors

All are also available in aluminium cladding for extra weather protection for those hard to service areas.

So if you are looking for some great high performance, high specification windows or doors then have a look at http://www.arugrupp.ee/window-and-door-production/products/facades-and-conservatories or give us a call.

Double or Triple Glazing?

The last post on Vacuum Glazing reminded me of another fact when looking at glazing. Most new glazing have a few energy saving features:

1. Glass coating (commonly known as low E glazing)
2. Low conductivity spacers (the material that keeps the panes of glass apart at the edges)
3. The gaseous fill in the glazing (argon and krypton are examples)

1. Glass coating is a good way of keeping heat in during the night time and winter months and the heat out out during the sunny summer days. The coatings can be applied as either a hard or soft coat, but given that the coating is applied to the inner glazing panel that is within the glazing unit there should be no real wear and tear to disturb its workings. These glass coatings are therefore a cheap and easy way to make your house a little more energy efficient (but the effect is quite minimal in the grand scheme of things).

2. These are physical structures that can help reduce cold bridging between the glazing sheets. This can be reasonably important when looking at high performance windows (but then the high performance window manufacturers know this and will fit them as a matter of course). But if you are specifying more standard glazing it is worth ensuring that you get these edge spacers as they are a physical attribute that will not decrease in their energy saving value over time.

3. The fill of windows actually makes quite a big difference to their performance. So having an argon fill is worthwhile, however be aware that the gaseous fill will, over time, dissipate. So after around 10 years the window will not be performing as well as it did when it was originally fitted. There is nothing that can be done about this, so maybe it is worth thinking about it all in a different way.

One way of getting similar performance to gas filled double glazing is to fit air filled triple glazing. The insulation values between the two are quite similar. Of course a gas filled triple glazed unit will be even better for the first 10 years or so.

Triple glazed windows are more expensive of course, this is because of the additional glass, weight and normally an enhanced frame size. The costs may never recouped from the additional heat load, however if you are trying to get a building to perform well and consistently then it might be worth investigating.

Note that triple glazed windows cut out some of the light coming into the building and if this is important then it might be worth considering installing double glazed windows to the more south facing aspects of the building (this will allow more heat and light into the building) and then have triple glazed to the north. The north facing windows will only even let heat out and so having these are higher performance windows makes more sense.

Vacuum Glazing

Pilkington Spacia is one of the new generation of high performance vacuum windows

Vacuum glazing has now appeared on the UK market and will be sold into the heritage market as a highly energy efficient option for windows where thin glazing is needed - sash windows etc.

On the face of it these are amazing windows, very low U values (so very good thermal performance) and easier fitting in thinner, older frames that cannot take modern double glazed units. So all well and good. However, there is a major issue that is not looked at in the brochures - Time.

Nature does not like a vacuum. So what happens to the window performance once the vacuum has failed?? Some of the manufacturers state that there is a 10 year guarantee period and that the windows are expected to last longer. To me I don't think that people will be aware of when the windows are no longer working properly and also the idea that you have to replace your windows every decade or so seems like a waste of resources / money.

I fear that this is a well intended energy efficiency exercise that might have unintended consequences. I think that it will lead to even poorer calculations in EPCs after a couple of years as they will be adjusted to take the windows original value, not its actual value at the time (this would be impossible to calculate easily). Later homeowners will be told that the windows are super efficient, but actually they will probably be very inefficient.

CADW have shown that single glazed windows can be improved radically by using secondary glazing, draught proofing, heavy curtains and shutters. So the expense of fitting vacuum glazing might be better spent on these improvements in the long run.