Heat Flow and Transfer
Heat flows from hot areas to cold areas. It occurs by:
- Conduction: When materials of different temperatures come into contact heat is transferred to the cooler material. (Spoon in hot water) Bulk insulation works by being a poor conducting material and being manufactured so it has trapped air pockets which are poor conductors.
- Radiation: All materials give off or emit energy by thermal radiation as a result of their temperature. The amount of energy emitted depends on the surface temperature and a property called the “emissivity”. On a sunny day, solar energy is absorbed by the roof, causing the frame and the underside of the roofing material to radiate heat down to the ceiling. Reflective barriers combined with bulk insulation provide protection from this heat. The reflective barriers work by reducing the heat going to the surface of the bulk insulation and therefore the heat flow through the insulation.
- Convection: When warm air moves to cold air it is named conductive heat flow. Bulk insulation restricts this flow by trapping the warm air in the pockets of the material restricting the flow.
When deciding on the best insulation for any environment the relative effect of each type of heat flow, which will depend on the materials in the structure, needs to be considered. An effective combination needs to be specified by a skilled specifier. Enviroflex staff have been trained in providing cost effective solutions to insulation problems.
Insulation Types
Bulk Insulation:
Polyester, Cellulose, Fibreglass, Rockwool
Reflective Insulation:
Sizalation, Thermaboard, Concertina Batts, Air-cell
All products supplied by Enviroflex have a four zero fire rating and can be fitted into any building structure.
Insulation Methods
Foil:
Foil is provided in rolls of 1350mm or 1500mm width. The Australian Standard that covers installation of foil is AS 4200.2 some points to note in installing foil as a sarking are
- Commencing at the lower edge of a corner of the frame. Foil should be stretched tight over the frame of the building the reflective side of the Foil to the inside of the building. It should be securely fastened to the framework by staples or specialized fasteners. Fasteners should be at 500mm centres.
- Next layer of foil should overlap by at least 100mm.
- All joins should be taped with specialist tape.
- Tape should be used to provide a weather tight seal around windows or any penetrations.
Sarking is an important part of the building structure providing protection from chilling winds and draughts. Heavy duty foil wrap is worth the additional investment in the product. Specialist insulation will ensure the product achieves maximum product protection.
An external cladding should be applied as soon as possible after the application of the sizalation, a check should be made as it is applied to ensure all penetrations remain sealed. Application of external cladding should not be within 2 months of fixing the sizalation.
Refer to material safety data sheet for the product being used but there are no known health or safety risks associated with sarking.
It is advisable not to apply on windy days as it is difficult to achieve a perfect result.
Smaller rolls (30 metres) will make the product easier to handle if there is no assistance available.
Thermaboard:
- Thermaboard should be installed to the frame after the fascia windows and plumbing are roughed in. Electrical wiring should be completed after installation.
- Top sheets should be fitted first pushing them up until they hit the underside of the rafters.
- “Board fix” Fasteners should be fitted at a rate not less than 3 per stud (5 recommended)
- The sheets should be butt joined (joins do not need to be on studs or noggins) and taped with specialized tape.
- Sheets should cover the top and plate by a minimum of 10mm.
- Window lintels should be covered.
- Corners need to be butt joined and taped.
- All penetrations should be taped to prevent any air infiltration.
Material safety data sheets for the product being used should be consulted but there are no known Health & Safety issues with Thermaboard installed in accordance with instructions.
Wall Batts:
- To reduce the cutting required make sure the batts purchased are at the correct width.
- Wall batts should be installed after the frame is completed, reflective wrap is fitted and all electrical & plumbing have been roughed in. This is usually prior to plaster.
- Batts should not come in contact with the skin of the building.
- It is best to start at an internal corner and to work around the external walls of the building.
- Ensure the batts being fitted are the correct thickness for the wall. If they are too thick they can push the plaster off the wall.
- Batts need to be ripped, cut or shaped to fit closely to the wall studs (5% of gaps can cause a reduction in efficiency of over 30%).
- The walls between garage and the house should also be fitted with bulk insulation.
- All gaps between window and door frames and the building frame must be filled with insulation or foam.
- A final check should be made to ensure all gaps are covered and the batts will not be compressed by the plaster. Compression will reduce the R value.
- Material Safety Data Sheets for the selected product being installed should be consulted. The use of Fibreglass or Rockwool will require clothing that covers all exposed parts of the body (A disposable set of overalls with a hood is recommended), face mask, Safety glasses and gloves should be used. This protection is nor required when using Polyester but the use of precautions such as safety glasses and a face mask are recommended.
- The most common question asked on Polyester is “How do I cut it?” The structure of the material means that it can be ripped across the grain (the width of the batt). It cannot be ripped in the length orientation. In 99% of cases sizes that are suitable can be made by ripping across the batt. If you need to make smaller, split the batt into thinner sections and then rip to the size required working through the whole thickness of the batt.
Ceiling Batts:
- To reduce the cutting required make sure batts purchased are the correct width (2 x 430 are used for 900mm spacings)
- Ceiling batts should be installed after the plaster is fitted and the electrical/heating/cooling and any other installations in the roof space are completed this is usually just before final clean. To reduce work the ceiling can be “loaded with packets of batts) prior to plaster.
- On flat or cathedral or limited access roofs should be fitted prior to plaster. They can be retained by the use of 12mm polypropylene packaging tape to support the batt until the plaster is fitted.
- Batts should be cut ripped or shaped to ensure they are a neat fit between the ceiling joists. 5% of gaps cab cause up to 30% reduction in efficiency.
- When fitting the insulation make sure the insulation does not cover the fans or downlights, clearances are specified in AS3999 at least 50mm clearance to be provided.
- Where possible ensure electrical cables are placed above the batts. Transformers should be mounted on the ceiling beams above the insulation and with adequate air circulation.
- Batts need to be placed right to the edge of the ceiling cavity, a stick with a nails in the end may assist to push the batts in these tight corners.
- Material Safety Data Sheets for the selected product being installed should be consulted. The use of Fibreglass or Rockwool will require clothing that covers all exposed parts of the body (A disposable set of overalls with a hood is recommended), face mask, Safety glasses and gloves should be used. This protection is not required when using Polyester but the use of precautions such as safety glasses and a face mask are recommended.
- The most common question asked on Polyester is “How do I cut it?” The structure of the material means that it can be ripped across the grain (the width of the batt). It cannot be ripped in the length orientation. In 99% of cases sizes that are suitable can be made by ripping across the batt. If you need to make smaller, split the batt into thinner sections and then rip to the size required working through the whole thickness of the batt.
Cellulose Insulation:
- Cellulose Insulation is applied with specialist equipment (Pumped) into the ceiling cavity. Each of Enviroflex installers have at least 10 years experience in professionally installing cellulose fibre insulation. They can ensure that the product is installed to meet the specified rating. That there is full coverage with no gaps and in conformance with Australian Standard AS4859.1
- Envorflex is the only company in Victoria to be able to offer a sealer for the cellulose.
- The sealer is vegetable based glue which provides a crust on the top of the cellulose. This prevents any problems with loose fill material moving in the ceiling or dust moving into the house. The sealer is applied 3-4 days after installation of the cellulose.
Air-cell Insulation;
- Air-cell insulation can be installed by the home owner. The installation requirements vary with the application. Please contact our office and we will forward the appropriate specification sheet.
Under-floor systems:
As the insulation is improved in the walls and ceilings of residences there is an increasing recognition that the floors particularly polished timber floors require insulation. All manufacturers of insulation have recognized the importance of this insulation and have developed products to meet the requirement.
“Floor Seal” has been developed for this application. Manufactured in 430 widths (floor space spacing) and 10 metre rolls, it is easily fitted between the joists and stapled into place. The rolls provide ease of handling less gaps to allow air flow. Polyester does not retain moisture and will dry if it becomes wet thus avoiding any problems with dry rot.
Care must be taken to seal the ends of the joists cut, Thermaboard is ideal for this application.
An ideal product for under floor application and retrofitting to existing floors. In new applications specialist clips have been developed to support the board. These are hung over the joists and the board is fitted in and held in place.
In retrofit situations battens are fitted each side of the floor joist. (They do not have to be the full length of the board) and the cut board is then slid into place. Care must be taken to seal around plumbing fittings and to provide suitable holes for any accidental water spillage to drain away.
Specifically designed for under floor application, air-cell will provide full sealing of the under floor cavity. Enviroflex can provide detailed instructions on request. (Be sure to put in the required cuts to allow any accidental water spillages to drain away).
These require supporting structures to hold them in position. Supporting structures used include fibre cement sheet and “chicken wire”.
- Rockwool Wall Cavity Insulation
Enviroflex Rockwool wall cavity insulation is an entirely dry system which uses granulated Rockwool, which is blown into the wall cavity at a predetermined density. The system is used to improve the thermal insulation of both new and existing brick veneer, double brick and some weatherboard houses, without having to remove the wall lining.
