Which insulation is best? It is the most frequently asked question during the Optihus founders’ year of operation. It has been received thousands of times, all with the aim of being able to avoid moisture, mold and smell. Here, a concise but still developing answer is given, with the opportunity to comment and share knowledge. A contextual answer is also given about which insulation is more environmentally friendly.
Which insulation is best for Australia?
The answer that the undersigned has given so many times during support and advice is that in principle you can use any insulation, only moisture aspects, health aspects and the function and limitations of the insulation are taken into account.
If you listen to the manufacturing parties, their product is of course the best. If you go to forums on the Internet, there are many opinions and instructions, many of which may actually be completely incorrect. Therefore, one should familiarize oneself with the subject area and investigate what actually applies.
For almost all existing insulation materials, there are no detailed moisture facts about what happens when limit values for relative humidity are reached, and what the user should think about when insulating risk constructions such as crawlspaces, crawl spaces, basements and attics.
Which insulation is best and what amount of it to use must be investigated based on the house construction to be insulated as well as surrounding and influencing conditions such as e.g. ventilation and moisture load.
Cell plastic Frigolit EPS
Cell plastic also called styrofoam or EPS is made from expanded or extruded polystyrene. The plastic material contains many air bubbles and thus acts as an insulator.
Insulation that goes by names such as cellular plastic, styrofoam, eps or styrofoam
Over the years, many areas of use have been developed. The picture here shows how cellular plastic was added as part of a less successful wall construction called a single-step sealed facade.
The single-stage sealed facade, inside and out, often consisted of wall cladding such as plasterboard, OSB wood fibreboard, building plastic, mineral wool insulation and wall studs, possibly one more fiberboard, the cellular plastic and mesh for plaster that was painted.
The single-stage sealed construction was condemned by the Supreme Court in 2015. The reason was contractor error which led to moisture damage. Moisture could leak in through leaks and then cause microbial problems as the moisture could not get out again. The construction plastic prevented drying inward and the cellular plastic prevented drying outward.
In addition to trapped moisture and mold and rot damage, it has been quite common for algae and mold to start growing on paint and plaster outdoors . Heat radiation from the inside is prevented and the plaster and wall paint are more affected by moisture than otherwise, especially towards the north and west, where the sun does not reach.
In response to mold problems in cold winds, some companies have developed EPS sheets that are laid under the outer roof covering of brick tiles, concrete tiles or sheet metal. The idea is to create a climate attic where the temperature is raised in the attic by moving parts of the insulation in the attic joists out to under the outer roof covering.
As the temperature increases, the relative humidity decreases. Even a one-degree increase in temperature reduces relative humidity by up to 6%, depending on the starting position. Klimatvanden’s cellular plastic insulation should be able to prevent otherwise common condensation on the inside of the outer roof during the winter months. In a climate wind, ventilation can be minimized, which means energy savings. Despite the better function of the climate wind, it is possible that active backup heating or dehumidification is needed in really humid climate conditions.
It has become relatively popular to cover the underside of the floor joist with the cell plastiolation as an additional insulating layer in crawl space and crofter ground. It is not the best crawl space insulation to use. The cell plastic prevents the bottom of the rope and the sills from drying out when moisture is trapped or leaks in. The crawl space under the insulation becomes cooler and more humid. At the same time, dehumidifiers cannot be used to dehumidify the floor joists and the overlying insulating layer.
An area that has become standard to use cellular plastic insulation for is under and around slabs on the ground, which today are called concrete slabs . EPS here provides good heat insulation and also moisture insulation against the cold ground. To avoid frostbite and for a draining effect, macadam is used under the cellular plastic. On top of the cellular plastic insulation shown in the picture, the concrete slab is then poured.
The majority of other solutions are also available where you e.g. casts cellular plastic between two layers of concrete or other firmer and load-bearing material. The insulation is also available as large hollow Lego pieces of cellular plastic which are stacked on top of each other as wall construction and filled with concrete.
The negatives are resource-intensive manufacturing, toxic styrene and substances for fire-retardant properties. In addition, several cases of fire have shown that cellular plastic can contribute to hard-to-extinguish and well-developed fires at the same time that the fire smoke is strong.
Some insulation materials are inviting to pests and insects . Some ants can gnaw on the EPS and make tunnels in the material.
Cellulose
A novelty from the past came back in the 1980s in the form of newspapers for insulating purposes. Cellulose, also called paper wool, consists of newspapers that are ground into a kind of wool which is available in bulk for manual laying or the perhaps most used form, blowing. The cellulose is also available as sheets.
The picture shows a cellulose sheet of loosely compressed and recycled newsprint. The colors for printing and printing black give the characteristic gray and color-changing shade.
Since the material originally comes from wood and is refined in several stages, it is quite susceptible to mold when untreated. To counteract mold and fire, certain substances are added.
Ammonia-like odors have been reported from some houses insulated with cellulose. Investigations concluded that it was due to added ammonium sulfate. Under certain climatic and moisture conditions, the ammonium sulfate, which is otherwise odorless, could dissolve as ammonia.
There is not much information available about this phenomenon, but some homeowners have spoken about it and there has been discussion between regulatory authorities and manufacturing companies. In the last case-related documents, possible replacement ammonium polyphosphate was mentioned. Even with that substance, full safety against smell could not be given.
Other products for construction that have been shown to emit ammonia are casein-containing floating putty.
Cellulose shares moisture properties with e.g. chippings, as the insulation can easily absorb a certain amount of moisture and then release it.
It is increasingly common in new construction and as additional insulation to use cellulose as loose wool for application in and on the joists in cold wind. When blowing in, the air must not be too moist and the insulation material must not be too moist either. Otherwise there is a risk that it will collapse and, despite the added inhibiting substances, become moldy.
There is also a risk that a cold bridge will form in the insulation layer where increased moisture content will result. It can especially happen where you don’t have a proper steam brake, e.g. construction plastic in the attic joists.
When newspapers etc. are recycled, there may be a risk that these are microbially contaminated, i.e. that they have been lying or stored where it is too humid and there are microbes. Newspaper recycling containers are one such place where it gets so humid that the upcoming cellulose insulation can be damaged. We do not know if the manufacturers control this or if all recycled paper is used regardless.
The good thing is that there are no insoluble and potentially health-affecting fibers in cellulose. Laying is therefore safer, but breathing protection should still be used as the insulation tends to dust quite a lot.
Sheep wool
Since time immemorial, sheep have served man in several ways. Not least, the sheep have provided meat and milk. In addition, the skin and wool have provided insulating warm and weather-resistant clothing.
At the time of writing, the thoughts go to the stories that exist about the Vikings. They, if any, really took advantage of what the sheep had to offer. The sheep’s wool clothing really provided warmth in grim autumn and winter climates by not releasing body heat too quickly.
Wool’s insulating ability can be used as an ecological alternative for insulation in Sydney, but some preparations are required.
The mutton roll is carefully washed and further prepared i.a. by adding a binding substance called PLA – Poly Lactic Acid. It is produced by fermentation of corn starch. The sheepskin is self-extinguishing, but for even better fire safety, fire-retardant substances are added.
The sheepskin has a high ability to absorb moisture but still maintain a good insulating effect. Even if up to 35% by weight of moisture has been bound up in the wool fiber insulation, the risk of mold attacking is low. In the wool there is a keratin that acts as an inhibitor on various microbes. Additional anti-mould properties are provided by the fire retardant additive selected, e.g. borax.
The added salt that borax makes up also counteracts insect attacks by moths, which otherwise thrive in the wool. Borax can be replaced with potassium nitrate in the production of insulation. It is desirable to avoid additives, but with wool it is not possible for the reasons mentioned. It is only during handling that one is exposed to these additives. Once the wool has been built in, the additive will mostly be bound between the wool fibers.
Despite the additives and washing procedure, sheep’s wool should be seen as a good and environmentally friendly type of insulation for houses. In 2016, it was estimated that there were approximately 600,000 sheep in Sweden. Together, these yield upwards of 1,800 tons of wool, based on shearing being carried out twice a year. It is a shame to throw away this wonderful opportunity to save nature several times over.