Optimo Underfloor Insulation

These are some of the common questions asked about underfloor insulation. If your question is not answered here, please get in touch with us.

What is underfloor insulation?

Underfloor insulation is applied to suspended timber floors in residential homes. Many homes with ceiling and wall insulation do not have their suspended timber floors insulated and these can contribute to significant heat loss in winter.

How does it work?

Bradford Optimo works like a blanket installed under your suspended floor; it inhibits heat loss which allows heaters to be used more efficiently. Optimo also helps to stop draughts entering through gaps in the flooring.

With an R-Value of R2.6, Bradford Optimo boasts one of the highest levels of thermal performance on the market to help keep you cosy during winter and keep energy bills down.

What is R-Value?

R-values rate the level of thermal resistance or the performance of insulation materials. Essentially, the higher the R-Value the more effective the insulation is.

What is it made from?

Optimo is manufactured from glasswool – the most popular home insulation product in the world.  The segments are specially stiffened and treated to provide a moisture resistant underfloor insulation.

The glasswool is made from around 65% recycled glass which is melted and then spun like fairy floss to create millions of air pockets. These air pockets are very poor conductors of heat, providing a cost-effective insulation.

Is Optimo safe for my family?

Bradford Optimo is made from inert raw materials that resist fire and pose no health risk to you or your family. Bradford is the only approved insulation partner of the Asthma & Respiratory Foundation NZ Sensitive Choice program.

Bradford Optimo is suitable for use in the homes of asthma and allergy sufferers. Optimo insulation does not provide a food source for insects or vermin.

Can Optimo be used on a concrete slab?

Yes, Optimo underfloor insulation can be used on a concrete slab when floorboards are being replaced or installed. When insulation segments touch wooden floorboards, they tend to dampen the reverberation of the timber and absorb some of the hollow floor sounds, making it sound and feel more solid. Optimo segments also help to insulate the floorboards from the cold concrete slab. Unfortunately, if leaks get through the floor, bulk insulation segments take a long time to dry. However, leaks can be offset by using good quality floor lacquer.

What is stopping mould growing on the sub-floor insulation in a damp subfloor area?

If you have mould within home you are likely to have problems within the subfloor or even within the building. In all cases, the source of the problem needs to be resolved. Mould will form on any surface given the correct environmental conditions: the right moisture content and warm temperature for the spores to grow, nutrient, light, oxygen, pH, time. If not treated, it will lead to costly repairs.

Optimo’s vapour permeability limits the potential accumulation of moisture on the warm side of the insulator. Without the accumulation moisture it is unlikely to provide the right conditions to grow mould. Furthermore the Optimo product prevents condensation entrapment as moisture will evaporate when homes warm floor warmth is provided. If the sub-floor area is constantly damp, and there are signs of mould on timber or other surfaces it is recommended to treat the mould growth and install an EcoFan(s), to increase sub-floor ventilation rates. If you have a very damp subfloor with signs of mould and water ponding on the soil, we recommend installing drainage, treating mould growth and increasing ventilation before installing Optimo™ sub-floor insulation.

How important is it for the segment to be installed up against the floor boards?

Section 5.5.3.1 of AS/NZS3999-2015 states that “Where bulk insulation is not installed directly against the underside of the floor, it shall be installed beneath the floor and held in place by a suitable support material or fixing device. Air exchange between the spaces above and below the insulation shall be prevented with particular attention at the perimeter of the installation and where structural members or other constructions interrupt the continuity of the bulk insulation”.

Any hole or gap through the insulator that provides an air cavity will allow convection air movement in and out of the air cavity that can reduce the effective thermal performance of the insulator itself. This air movement can further by magnified with the effects of external wind pressure moving air in the subfloor zone. The thermal loss will affect the full length of the particular corridor bay that has this draught. In regards to vermin, once within the air cavity they have unrestricted pathway to travel the length of each bay.

What happens if I have rodents?

Glasswool is made from inorganic material having a base ingredient as sand. There is no nutrient within the product. Vermin drill through an insulator material to see what is on the other side; search for food or shelter. Bradford’s product solution is to position Optimo against the flooring material to prevent cold or hot air by-passing the insulator. This product position makes it difficult for vermin to travel horizontal distances. However, it is recommended to address the rodents before they enter other parts of the home cavities.

What happens when it rains on the floor boards during construction and the chipboard floor leaks water through to the segment?

Bradford’s formulation for the Optimo™ sub-floor insulation allows water to drain through the segment’s fibres known as an open lattice structure. Once dried out and restrained will return to its original performance. Its high vapour permeability prevents condensation entrapment that can occur on other alternative subfloor products. Alternative subfloor insulators that introduce drainage or perforations to improve vapour permeability incur the loss of thermal performance as a result of air convection movements bypassing the insulator.

How do the fixings work to secure the insulation in place?

Bradford Optimo™ sub-floor insulation segments have been manufactured with increased binder content to provide rigidity. The size of the segment (415mm or 565mm widths) has been designed to friction fit between the joists of suspended timber floors, which are constructed at standard spacings (ie: 450mm or 600mm centres). Correctly fitted, the segment will be held in place, however straps or saddles are recommended to be used for reassurance that the segment is secured in place. Fixings are recommended on both side edges of the segment 3x fixings per segment length.

What happens when the depth of the joist is greater than the segment thickness?

For a retrofit project, simply bend straps into an L shape, at 90°, and fix it to the side of the floor joist. Fold the horizontal leg upwards to support the segment fitting tightly against the underside of the floor.

For a new home installation, there are no additional requirements.

What width do you cut, if the segment is too tight to fit between the joist spacings?

Trim the edge to 5mm over the width of the space before inserting.

What do I do if the joist spacings are non-standard and the segment is loose?

Slice a piece of insulation off the edge of another segment and use it as a side edge packer to secure the segment between the floor joists. Additional fixings will be required to support both pieces.

Are there any concerns regarding electrical wiring?

If any electrical wiring will be covered by insulation, seek advice from an electrician as cables and equipment partially or completely surrounded with bulk thermal insulation may overheat and fail. Additional advice should be sought for any electrical wiring installed pre 1989. Electrical wiring can be buried with Optimo as long as the cable is in direct contact with a substrate such as a timber joist, otherwise wiring is limited to travel through a thickness of no greater than 300mm of bulk insulation. .

What does the AS/NZS4859.1 compliance mean?

Bradford Optimo™ sub-floor insulation is manufactured under ISO 9001 Quality Systems and complies with AS4859.1 “Materials for the Thermal Insulation of Buildings”. This is your assurance it will provide the level of performance stated on the pack. When comparing alternative products, ensure they comply with this standard before comparing alternative product material R-Values with Optimo’s material R-Value. Advertised Total R-value must match the projects subfloor construction and ventilation properties.

What guarantee will there be?

The Optimo™ sub-floor insulation product itself is covered by a 70 year performance warranty.