Inside out: the wrong way round

When we move into a new house we tend to do two things:

1. Complete the work detailed in the mortgage agreement (this tends to be things like damp proof courses, underpinning, roof repairs);
2. Decorate in order to make your mark on your new property.

So what you are left with is a nice looking internal environment and a structure that a finance institution is happy with.

There are some issues with this.

1. Firstly, finance companies do not understand the workings of older solid walled properties and so many of their recommendations are pointless / potentially damaging. The money spent on these measures could / should be better used using more permanent solutions, but this is a huge topic that is impossible to deal with in this short post.

2. Decorating over issues like mould, damp, cracks is pretty pointless unless the root cause is also dealt with. I have seen this over and over again where people have spent a lot of time and money making their mark only to find that the mould / damp / cracks re-appear. This is the point of this post.

We would recommend using those initially tight resources to solve the problems with the house. These issues are not limited to what the mortgage company says, so don't be lured into a false sense of security. Use this blog to flush out some potential problems (the indicators are things like dry lining, freshly painted walls etc.)

Most of these issues tend to be on the outside of the house, hence the title of the post! The majority of what needs to be done to a house, in order to make it fault free, is based in chronic poor external maintenance. So have a good look at things like:

• Re-pointing
• Cracked / blown renders
• Raised ground levels
• Blocked vents
• Blocked / broken / faulty guttering
• Rotten timbers
• Flashing around chimneys
• Chimneys not protected from rainwater
• Silicon failure around doors and windows
• Incorrect paint being used on solid walls
• Poorly sealed walls around incoming / out-going services

Once the outside of the house has been maintained properly then you can decorate to your hearts content with the knowledge that it will not fail in a few months time.

Remember that in order to keep your house looking good and operating well you will need to use the correct materials and products. Reading this blog will help with that. Also it is worth noting that maintenance is a regular requirement and not just a one off. So every now and again have a good once-around the outside of the house to ensure that all is well; it is easy for guttering to get blocked / fail and for new cracks to appear in cement render, etc.

CADW have a really good website on maintenance. Don't be fooled by the term 'historic', as this applies to all solid walled buildings. See http://www.maintenancematterswales.org/

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.

MVHR insulation

I was in a meeting for the Existing Homes Alliance Cymru and we had a good presentation on the Project CALEBRE research from Loughborough University. One of the issues that they had in their work reminded me of another couple of cases I have seen with the installation of MVHR in homes. MVHR is Mechanical Ventilation Heat Recovery, so a system that ventilates your home with fresh air, but does so by using the warm and moist extracted air to pre-heat the incoming air.

One issue is that of insulation. In the Loughborough case, and in the two I have seen, the insulation was really poorly fitted around the ducting. It was there, but the corners were not covered properly and the pipe lengths were not wrapped up and sealed properly. This of course means that the warm air that you need to pre-heat the incoming air was not as warm as it could have been and also the then pre-warmed air was losing some of its heat in the loft space. So take care when having MVHR installed and make sure that you check the quality of the installation afterwards.

Two other issues emerged from the Loughborough study that are also really important.

1. It was found that the system was not calibrated correctly for the house as the installer did not check this until they were called back to sort the insulation problem. So it sounds as if this is not necessarily done as a matter of course. So ask your installer to check the settings once the system is up and running (with the insulation correctly fitted).

2. The cost savings that can accrue from using a MVHR do not kick in until you have a really airtight house. So unless you have an airtightness level of around 3 cubic metres per sq m per hour or better you will not get any carbon benefit. Having spoken to Ventilation companies they tend to state that MVHR can be installed in houses with an average 7 - 10 cubic metres per sq m per hour. Whilst this is true they can be fitted, it will not give you any cost or carbon benefit, so it is not worth while. Most new houses are built to a standard of 10 cubic metres per sq m per hour and so using MVHR in retrofit is really tricky to get right.

Walls adjoining houses - a source of damp

Many homes have garden boundary walls that butt into the main external wall of the house. The continuity of the materials can look really attractive, especially where it is an old stone wall. There can be complications though with the junction between the two structures.

We look to keep our houses dry and free from damp, but we do not expect the same from our walls. So we tend to turn a blind eye to the water that seeps into the garden wall, whilst desperately trying to keep water from entering the wall.

This has led us to applying waterproof render to our house walls and nothing on the boundary wall. The trouble is that if there is no capping on the garden wall, water will seep into it and this can then be transferred through the junction of the two walls and thence behind the water proof render.

This is normally 'cured' by injecting silicon vertically into the house wall, but it stands little real chance, especially in stone. So what to do?

Well, ideally your house walls are treated with lime render and so can breathe and let the water out, however this is making the lime do a lot of work. The best two scenarios is that you either reduce the amount of water entering the garden wall in the first place, via a simple capping system; or that you create a physical gap between the two walls.

If you choose the latter then be aware that the house wall would be giving the garden wall some inherent strength and stability and so this will probably have to be replaced by the use of a buttress type support in order to stop it all from falling over!!

Sagging roof?

One of the great joys of thinking about buildings is that you tend to remember to look up. So many of our high streets are regarded as being the same these days, but a glance above the signs that carry the all too familiar names and you will find a wealth of architectural interest. Keep going up and you will notice that many of our older houses have one of two main roof coverings: slate or tiles.

When the buildings were originally designed and built they would generally have been covered by slate. Most of this came from the quarries in North Wales of course and the history of this industry still covers large swathes of Snowdonia National Park.

However the modern day knock on from this is as follows. The roofs were originally designed and built to take the weight of this material. The industry, of course, does not stand still and soon cheaper alternatives became available in the form of cement and clay tiles. As with most things in the industry these cheaper alternatives were quickly taken up and applied to roofs everywhere. Unfortunately this has meant that older roofs, that were designed for slate, find themselves with the much greater task of supporting these heavy tiles. It is therefore quite common to see roofs bend and buckle under this weight. So if you are looking to replace a roof please think about the weight of the structure as well as the look. Note that if you do have a sagging roof, you will also need to check for rot in the timbers, damp ingress, movement in the wall plate, wall movement etc.

Thankfully, if your budget doesn't stretch as far as real slate there are a wide range of artificial slates that are available now that look like the real Welsh slate, but are in fact made from recycled materials.

Chemical damp proof course holes

As you may have gathered by now I have an issue with damp proof courses in older walls, however they do have their place and one of these is in brick walls. Here damp proof injections stand a chance of working as long as they are applied correctly. The silicon creams can flow into and along the mortar layers (in lime mortar) or into the bricks (in cement mortars).

The process for this is to drill out a hole for the injection gun and then to inject the cream or liquid into it. The treatment will then go into the structure and create a water proof layer (well in theory, there are some issues here with how totally effective it is, but that can wait).

All well and good, one might think. However I have seen time and time again a major flaw. Contractors, having created this water proof layer, are then meant to back fill the hole with a sealant (this might be cement, lime, plug or a silicone filler) but so many do not. This this effectively creates a system where rain water is allowed into the structure above the water proof layer! How ridiculous is that?

So if you do have a damp proof course injected into your wall, just check that the holes have been back filled. Also because most often they use cement to backfill this can often be pushed out of the hole as it is incompatible with the underlying mortar or brick.