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.

How much insulation is it best to use on solid walls?

Wood fibre board insulation being used externally

Many of you will be aware that I am slightly reticent in recommending certain insulation types on older buildings. This is because of the risks associated with damp, thermal bridging and structural failure. So assuming that you are planning on using a breathable insulation (like wood fibre), how much should you apply?

The Part L of the Building Regulations wishes any refurbishment to get to around 0.3 - 0.35 U value for a solid wall. It thinks that all solid walls have a starting value of around 2.1 which is actually normally much worse that they are. This has led to companies putting on around 120mm thick insulation. Knowing the starting point of your wall is really important as thick walls can be as low as 0.8, so around three times better than predicted. In Wales most solid walls are around 300mm thick and these have an average of 1.51 (from Caroline Rye). So around 30% better than predicted.

In order to get Building Control approval for anything more than 0.3 then you will need to cite that this is a breathable wall and hence special considerations are available for it.

The recommendations I would give change depending on whether you are applying External or Internal Wall Insulation. The base reason also changes.

External Wall Insulation (EWI)

The situation with EWI is that whichever material you choose the real key is to get thermal bridging and rain protection sorted. Reveals, roofs, rainwater systems, etc are all really important to get right. It can be more effective to put 20mm over all the surfaces (inc reveals) than it is to put 100mm just over the walls (not in the reveals). So it is key to get the specification and detailing right.

The more insulation you put on, the less effective the insulation becomes in relation to its thickness. This means that the first cm of insulation reduces heat loss the most, the second will provide less heat loss, the third less still. So there is a rule of diminishing returns at play at here. So there is no point putting on loads of insulation when you will get a similar return from less. As a rule of thumb here to get down to 0.3 you will need 100mm of insulation, However, this assumes that you are starting with a U value of around 2.1. So if your wall is 1.51 then you should be able to use a 80mm board, but remember to put on the 20mm reveal boards!

Even with a breathable system you will need to ensure that it is weathertight. So make sure that the required work is done to rooflines, eaves, guttering etc. 

Any EWI needs to have a protective covering and again this needs to be breathable and also long lasting and so we would recommend a lime render combined with a lime proof mesh and a breathable paint finish (silicate paints are ideal for this).

Internal Wall Insulation (IWI)

Wood fibre board installed internally (from Inglehome)

IWI has the consequence of making the outer side of the wall colder and this can lead to a number of problems including damage from freeze / thaw. Using a vapour membrane also draws in moisture into the wall, so it is really important to use the right insulation system here. Breathable systems can be used without a vapour membrane (unlike the conventional insulation systems that either have built in vapour control, or require a separate membrane). This lack of barrier makes the system a lower risk in the long run.

Research is showing that a safer U value to aim for, is around 0.7 to 0.8. This means that many thick walls may already have this type of value and so not need any insulation. However, most walls are around 1.51, so in order to get down to 0.7 you only need 40mm of wood fibre board. Having a wall that allows a little more heat through it than recommended by Part L is important as this helps to keep the wall dry and safe. 

If installing IWI it is also really important to remember thermal bridges. So reveals, between floors, fold backs along party walls etc need to be assessed and treated appropriately.

If using a wood fibre system you would need to use a breathable finish on the walls. So a lime plaster skim and a claypaint would be ideal.

The failure of ECO

From Nick Heath / English Heritage report

A great report by Nick Heath for English Heritage is available that looks in detail at the issues raised by large scale retrofit. There are a number of horror stories there waiting to happen, but at least Nick has managed to create a guidance tool for local authorities to help them get over the many issues associated with these large scale 'improvement' projects.

One of the main troubles with ECO funding for External Wall Insulation (EWI) is that they only cover insulation measures. Nothing else. This means that lots of practical issues are not addressed. For example in the picture the insulation could not be fitted behind a lamp post because there was no money to move the post. This meant that there is a huge thermal bridge in the wall. This then causes a range of problems with damp, condensation etc and also means that there is a large impact on the effectiveness of the insulation.

I was in the SE Wales valleys last year doing some training for CITB on pre 1919 buildings and the same was happening there. ECO would not pay for roofs to be extended to provide the required protection for the insulation. So instead the contractors were required to install some plastic caps over the insulation. This relies on mastic / silicon sealant to provide long term protection from water ingress. The insulation system is therefore not guaranteed as it is not fitted to the manufacturers specification. The caps were supplied by other people and so there is a huge issue of future responsibilities when the water gets behind the insulation.

I feel sorry for the organisations installing ECO as they want to do a good job, but the ECO funding means that they just don't have the resources to do it properly. Of course the owners of the houses could pay for the work, but the whole idea behind ECO is that it is for those people who are disadvantaged and hence don't have the thousands of £s required to make up the shortfall.

One gets the feeling that many of these large scale EWI will fail and then cost an arm and a leg to put right. So in our drive to save carbon we are in fact probably going to end up having to pollute more. What a shame.

There are ways of doing this work at a lower risk, but it does cost more and requires a more skilled workforce. In the end, though, it would save more money, but the systems that the industry is forced to work to means that this will not happen. We will continue to have schemes that are underfunded, ill specified, done poorly (due to inadequate underpinning knowledge of materials and thermal dynamics) and also done at the wrong time of the year (most of the ECO work is done between November and March due to funding requirements).

A tad depressing, but I think that we need to know the issues so that we can try to ensure that we stop making the same old mistakes.

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.