by Stuart Thomson

In this third article of the series Stuart Thomson looks at the effects that modern ideas about insulation are having on what we see as a serious problem in complaints of “leaking” and “condensation”. Since the last article we have had a couple of meetings with interested parties and an investigation by BRANZ is starting off. After the last article on ventilation, we had quite a large number of emails supporting the fact that there is a problem. I would ask any reader with a case of “leaking/ condensation” which can be looked at by the BRANZ team to send details in via Scope. As usual I have to add that while the main drift of this article is in line with our current investigation, some of the comments are Stuart Thomson’s and not official policy. Stuart Hayman MRM Technical committee.

The last two articles on underlay/ condensation/ ventilation have drawn much positive feedback in spite of swimming upstream against the official flow. Roof cladding is no longer just a product- it is a roof system.

Insulation is not new. The Egyptians knew about it and they built with thermal mass to even out the high and low temperatures of the day and night. Many countries build to keep the heat out rather than to keep the heat in but in New Zealand we usually insulate to keep the heat in and have generally opted for thin wall construction and cold roofs. (A warm roof is where the insulation is adhered to or formed onto the  Metal roof cladding)

The Vikings and other Europeans learned that by insulating their homes with mud reinforced with dung and straw and plastering in between the cracks of the logs they gained a measure of airtightness and comfort. They also knew that fur was good for clothing to insulate their bodies. We now use synthetics like polyester and natural insulators like down.

Many years ago when working on some old houses in the Chinese district of Tory Street, Wellington, the writer was surprised to find all the outside walls stuffed with crumpled newspapers and old pakapoo tickets. (An old Chinese gambling game) As insulation it was cheap and efficient and available. While insulation is not new, the standard of comfort now demanded appears to follow that set by the World Health Organisation (WHO) at 65° F -18° C and all recent reports seemed to be based on this premise although UK has gone with 15.5° C.- 60° F.

While it is easy to find that the majority of New Zealand homes generally do not live up to this expectation there is little proof to link health with temperature alone. Comfort has been confused with health and, what appears to be lost sight of is, that it is mostly the moisture content that determines people’s health. (Except perhaps in the very young and very old.)The higher the air temperature the more water vapour it can hold.

The drive for insulation and the recent government support by way of subsidy has seen the retrofitting of many New Zealand homes with ceiling insulation rather than wall insulation, which is in the too hard basket. To trace the history of insulation in New Zealand may give some insight into the reasoning (or
otherwise) of the move to subsidise heat pumps and ceiling insulation. The first published data on a
measure of insulation for New Zealand homes came from Dr Lyndon Hastings when he wrote ‘Handbook on the insulation and heating of buildings’ in 1958. This led to his recommendation in 1964 as shown in the table. The local manufacture of fibreglass began in Auckland in 1961 and Winstone Ltd. were one of the first to offer a home insulation service.

Then in 1972 the Christchurch City Council introduced an insulation by-law for new home insulation but this was more about the polluting chimneys and alternative heating than insulation. Since that time we have upped the anti, as shown in the table, but we are still a long way off other countries recommendations.

Insulation is traditionally measured as an R-value; the thermal resistance to the passage of heat measured in m2·°C/W; the higher the value the higher the resistance. In the United States R-values are approximately six times SI R-values A U value is a measure of conductance which is the inverse of
an R-value.

The following Table ( page 16 ) uses N.Z.R Values based on Zone 2 Australian R-values based on Zone
6 (Coastal Victoria) * Dark roof (darker than Desert Sand. Lighter than Bone white = R 4.1.) U.S Equivalent R values (US values in brackets) based on Zones 4 & 5 ( mid – US)

In 1975 the government introduced interest-free loans for insulation and the Housing Corporation followed
shortly after, using macerated paper as a ceiling insulating material. The world energy crisis encouraged
the quest for insulation. Our low hydro lake storage made it evident that hydropower was not so free and or available as previously thought and it was logical that energy savings would have to follow. But it was the escalating cost of oil and New Zealand’s dependence on imports that finally drove the government to legislate for compulsory new home insulation in 1978.

So what was the motivation? Was it energy saving, less air pollution, creature comfort, health or just great advertising? If you guessed a bit of each you probably would be about right. Don’t get us wrong. Insulation is a good thing but there is a balance of airtightness, ventilation, solar design, cost and user savvy that is equally important for our countries economy and the health of our homes and their occupants.

While we live in a global village and nothing we say, do or act upon is done in isolation, we must look at
New Zealand as a special case. We are a unique island with a unique climate and we think we are a unique people. Actually the latter is not entirely true as we are pretty gullible lot and believe what the advertisement says and particularly if an official report has EECA’s or BRANZ’s name on it.

The carrot of a free thousand dollars or so was too much for most New Zealanders to miss and so many of
us paid out a lot more to insulate our ceilings for a feel-good factor of saving energy. But did we ever do
the true cost/ benefit analysis?

Do you remember that ad when the attractive young lady came home from work and took off most of her
clothes because the ceiling has just been stuffed full of the pink stuff?

The problem was a psychological one, “now we are insulated we can crank up the new heat pump 3°or 4°.” The problem was that although the ceiling was insulated, the walls and windows were not. We upped the air temperature and its capacity to hold more moisture but we dare not open the windows because we would let all that “new” heat out! Even the best aluminium double glazing E-glass, argon, the lot, has only 1/6 of the R value required for the walls!

But insulation is not just about houses it’s about people too. Skinny people feel the cold but the overweight don’t seem to notice it. Normal people react to what they have become used to, those raised in a cold climate know their seasons and dress for them. New Zealanders are not good at ‘dressing up’ for their climate. The Americans are worse so while we tend to wear short-sleeved shirts in the summer and wear a jersey in the winter they do the opposite, because everything is so coldly air-conditioned in the summer. More energy is used in the US for cooling than for heating!

Humidity is a major factor for thermal comfort which is very much dependent on whether the skin is wet or not. Over the years as technology has provided us with solutions, the current demand for a more comfortable environment is now narrowed down to a very small band of temperature. Our extremities are very sensitive to cold environments and we insulate our fingers with gloves and our toes with thermal socks and protect our nose and ears.

While there are different forms of heat insulation such as loose fill, rigid board, blown and spray foam, the most used NZ insulation is fibre, either rock, polyester, wool or glass fibre segments or blanket - which this article assumes. N.B. The term ‘Batts®’, although commonly used, is a registered trade mark of TINZ Tasman Insulation and the term “segment” is the alternative word. Sound insulation is also obtained by using some of these materials in a denser form. Foil is often referred to as an insulation material which it is
not, because although it can reflect heat it relies on a still air space to provide any insulation benefit.

Insulation is the stuff that keeps hot stuff hot and cold stuff cold. It is easy to forget that the prime purpose of any insulation is to provide still, trapped air which is a very good insulator. A Thermos is an even better insulator but it has no air - just a vacuum.

While retrofitting an attic ceiling insulation is relatively straight forward, it is inevitable that some areas around pipes, electrical fittings and especially at the wall/ roof intersection the fitting will be less efficient than in a new dwelling. Retrofitting skillion ceiling insulation can only be economically installed when reroofing with the task of designing and fitting insulation usually falling to the roofer.

Most heat loss across an uninsulated air space is by convection caused by differences in temperature and the purpose of the insulation of the cavity is to slow it down. However there are still losses due to  conduction and heat transfer through the framing. The natural law of equalisation is a hard one to beat.

So just how good is this insulation? It is not often recognised to the extent that the R-value applied to a
product has to be depreciated by other factors to obtain the actual R-value of the wall or ceiling with the insulation in place. There are heat losses due to the framing and by compressing fibreglass as the ‘nip and tuck’ methods of some installers save money by using up small pieces or jamming the insulation to avoid cutting. More particularly though losses are due to the gaps left by the installer. A gap of 6% of the cavity = 20% efficiency loss (NRCC.)

Another major loss factor not often considered are downlights which not only downgrade the R-value but allow moisture laden air into the attic space. If you have one downlight for every 2m2 of ceiling then your R2.9 theoretical ceiling value drops to R2.1! Because the R value of single glazed windows is only R0.15  they let out 10 times more heat than the wall. If the total glazing area of your East, South and West walls is
> 30% of the total wall area then you will have to compensate your design. New buildings require R0.26
for glazing in all areas however it is still possible to design using single glazing in some areas by compensating. Solar gain and free passive heating comes from the North but so many of our New Zealand homes are oriented to the road and not the sun. Developers take note. And don’t carpet those North rooms that have full length glazing- remember thermal mass. While lined curtains are insulators and a good investment they are only as good as the gap between the two pieces of material. That’s why pelmets are a good idea to stop the convection currents. But don’t forget to pull the curtains early in the evening in the wintertime. Where you live in New Zealand will determine what minimum insulation values are required by the NZBC H1/AS1 and how much you have to pay for heating. Of course the house orientation, design and occupants will have a major bearing on these dollars to. Also more heat is needed to heat moisture laden air. A look at New Zealand’s large cities in the NZBC three insulation zones gives some idea of those differences.

Wet insulation is no installation; the three legged stool of underlay, ventilation and insulation means the
whole roof system has to work if condensation and wet insulation are to be avoided. If there is no attic
ventilation, underlay can accumulate moisture on the underside and if there is enough of it, it will drip and
wet insulation. Another detail which always causes problems is when the insulation is compressed over the top of the purlins. The NZMRM Code of Practice has never sanctioned this detail but unfortunately this is a
BRANZ recommended detail.

This drawing, that follows the BRANZ detail, was very recently consented by a South Island BCA, flies in the face of good trade practice, the NZMRM Code of Practice NZS 4246:2006 and even the manufacturer’s
recommendations. The Roofer is stuck between a rock and a hard place. He is required to sign off the
Record of Work for a CCC (now a Consent Completion Certificate) knowing that there is a good chance
that this detail will fail!

There is no way the fire retardant absorptive underlay can dry out and this detail not only voids any R-value but over time the roofing screws become loose and cause leaks. So who carries the can? Installation works best when there is not a lot of air able to pass through it. Heat is an escape artist and like sound, if it can find a gap it will escape! While we need to build tighter to save energy costs we must be careful that we do not make homes air-tight to the extent that fresh air is excluded and moisture retained.

One problem that has occurred since the 2007 increased requirements of H1/AS1, is that in the very popular skillion roofs, there is just not enough room left to place the fibreglass insulation and still maintain a minimum 20 mm air-gap. Another problem associated with dimension is the property of fibre insulation to loft. Lofting is the term used to explain the growing in dimension of insulation once it is released from its compressed bale and the manufacturer’s use- by date has some bearing on this.

The problem is compounded because different fibreglass insulation manufacturers make their segments and blankets in different densities or a different thickness for the same R value. This is a design problem. When considering design substitution It is not permissible to interpolate or extrapolate product R-values because fibreglass is manufactured in different thicknesses and densities.

What this means is that substitution must not be made without checking the design and if change is needed then an agreement between the BCA and other parties must be reached prior to any work being

Two manufacturers have recently recognised the skillion problem and produced denser SRB’s - skillion roof batts® or blankets. However attention must still be paid to ensure that at least 20 mm of clear space is left above the insulation for separation from the roof underlay to allow it to dry by attic space ventilation. (this was described in the previous issue of Scope). Why do we not have a Standard for insulation size and density?

H1/AS1 2007
There are many forms of heat but one above all is the most comfortable. It is radiant heat. The sun is a radiant heater and doesn’t heat the 93,000,000 miles of space in between us. If a wall or a floor is warmer than you are then you will feel warm, if they are colder than you are you will feel cold. To the writer, forced air convection heaters such as a heat pump, are uncomfortable and unhealthy. For one reason when air is used as the vehicle to move heated air through the house it distributes mould spores, mites and dust; the other is that one’s head becomes flushed by contact with moving and dusty air directed by a noisy fan. Radiant heating from a heated floor is the reverse as your feet become warm and your head is cool. The Romans knew about radiant floor heating which is now known as hydronic heating and acknowledged (at least in Europe) as being more efficient than forced air systems.

In 1968 the writer built one of the world’s first 400 solar heated houses. This had a radiant floor with solar hot water being circulated throughout the house giving the floor temperature in the low 20°C’s. The house did not have fibreglass insulation but did have a ceiling reflective foil dead air space. The view was to the south with large aluminium doors and joinery so the air temperature inside certainly was not 18°C.! The house however was warm because you felt warm because the floor was radiating heat. European experiments have shown that school class rooms with lower air temperature but radiant floor heating, enabled their students to score higher than their classmates in a classroom using convection air heating.

The roofing industry has nothing against insulation per se, but it does have a gripe about what the added 50% of insulation has done to increase the condensation problem in unvented attic and skillion roof spaces in the last five years. This is not an insulation problem it is a design problem. Not only are we experiencing an increase in construction problems but in spite of increases in air indoor temperatures asthma is on the increase as well. An insulated roof system needs to be designed holistically with not only insulation but the airtightness, heating, ventilation, moisture sources, RH and air quality all considered at the design stage. The energy loss by venting above the insulation to minimise condensation has to be weighed up on a cost/ benefit basis as the most cost effective solution may simply be to offset the loss by increasing the ceiling R-value. Infiltration and ex filtration rates need to be known.

One problem job came to a deep south homeowner who recently had his hot water cylinder supply tank
in the roof, suddenly found he had a leaky home — not from the roof but from his water pipes that had
frozen. Why had this happened only at this time?

Like many others he had taken advantage of the government’s insulation offer. The heat leakage from the roaring fire in the living room had kept the attic temperature above freezing but after the installation of insulation, the attic space and the metal roof temperature dropped below freezing long enough to burst copper pipes on thawing and give him a condensation problem he did not have before.

Another problem job involved a complaint of wet insulation in a new residence which as usual was blamed on a leaking roof. The excessive construction moisture came from the curing concrete slab and the drying out of the framing with moisture escaping into an unvented roof cavity.

Yet another problem job involved an owner who took advantage of the government’s offer of insulation and heat pump subsidy... but at the same time turned his basement into a flat but without a heat pump. Not long after the renovations, mould began to grow in the south facing bedrooms of the upstairs flat. Yes, his heat pump was too small to heat the whole house and yes there was no attic space ventilation.

This situation was resolved when the writer discovered an unflued gas heater in the bottom flat which allowed water vapour (heaps of it) to find its way upstairs. The owner was persuaded to buy his tenant a
heat pump and wrote his tenancy agreement so that no gas heaters were permitted.

To help us solve our excessive moisture problems we need action.

Let us be blunt; - ban unflued gas heaters now. Besides moisture they produce carbon monoxide and
nitrogen dioxide - not a good idea. Portable gas heaters may be cheap to buy but they are expensive to
run. Placemakers won’t sell them! They are already banned in Western Australia, Victoria and Queensland,
Canada and some U.S. States. It is said the 35% of NZ homes have them – perhaps that is why we have
so much asthma?

If you need a dehumidifier you have got a moisture problem.

Let us also ban those so-called heat recovery positive pressure systems that do not have a fresh air source
and a heat exchanger. They circulate stale air. The recent ECCA report prepared by the University of Otago agrees (quoted in the last issue of Scope). We also need to look closely at the use of VCL’s (vapour
control layers) to prevent moisture migration into the roof space and revisit the problem highlighted by Harry Trethowen in 1988 on sub floor moisture migration.

Over two thirds of New Zealand houses were built before insulation was required and 80% of these were single detached dwellings which still do not have any floor or wall insulation. N.B. A building consent is required to insulate walls. Unfortunately these are the problem houses with families with health problems that we should be directing our insulating subsidies towards. A unhealthy home has unhealthy children.

You may not believe or agree with all what you have just read but do read on…..

A graduate architect returned from his OE. He married and built a modern house with carpets, aluminium windows, insulation, heat pumps - the lot and took a good job with a large architectural practice. Two boys were born but unfortunately both soon developed asthma and used puffers, had consultations with doctors and specialists but to no avail. After 10 years the architect wanted a major change of lifestyle and a decision was made to go into practice on his own account. Money was needed for an office and so the
new house was traded for an old villa in Ponsonby. No carpets, two chimneys, wooden windows and no
insulation. After six months the two boy’s asthma had disappeared.

Not many dust mites?
No mould spores?
A lot more fresh air?