Straight answers to the questions South African homeowners ask us every day: cellulose fibre versus insulation rolls, batts, R-values, electricity savings, rodents, spray foam, fire safety and what happens during installation.
No sales talk or complicated technical language, just clear, practical advice to help you make the right decision for your home.
Thermguard has spent decades manufacturing and installing cellulose fibre ceiling insulation for South African homes. Browse the categories below to find the information you need, or start with the most common questions answered directly on this page.
Genuine reviews from Therm Guard customers across South Africa.
Many homeowners have only heard of traditional insulation rolls or batts and want to understand why we recommend cellulose fibre ceiling insulation. That is a fair question.
The FAQs below cover the questions we regularly answer over the phone, during home assessments and at the roof hatch. They are grouped into clear categories so you can quickly find information about comfort, energy savings, R-values, safety, pests, moisture, installation and different insulation systems.
If your question is not covered, speak to a Thermguard expert for a straightforward answer based on your home, roof type and insulation requirements.
For the real-world experience, you can also learn more about why homeowners choose Thermguard and read feedback from customers who have already insulated their homes.
Thermguard is a loose-fill ceiling-insulation product manufactured primarily from recycled newsprint. The paper is processed into light cellulose fibres and treated with inorganic salts to improve its fire performance and make the material unattractive to insects and rodents.
The finished product is blown onto the ceiling rather than supplied as pre-cut boards, rolls or batts. This allows the installer to distribute it around roof trusses, ceiling joists and other obstructions. Thermguard states that approximately 80% of the product is recycled newsprint and that it is manufactured in South Africa using a low-energy process.
Heat naturally moves from warmer areas to cooler areas. During summer, heat from the roof moves towards the cooler rooms below. During winter, heat generated inside the home moves upwards towards the colder roof space.
Thermguard’s fibres trap small pockets of air, slowing this heat transfer through the ceiling. Because it is blown into place, it can form a continuous layer around many of the gaps and obstructions that can be difficult to cover with pre-cut insulation.
Insulation does not generate heating or cooling. It helps the home retain the temperature created naturally or by heaters and air-conditioners for longer.
Loose-fill cellulose can settle slightly after installation. This should be allowed for when the product is specified and installed.
The required depth should be based on the product’s settled density and the R-value that must remain after settling—not simply the loose, freshly blown depth. Correct installation therefore requires the contractor to apply enough material to achieve the specified settled thickness.
Normal settling is not the same as product failure. Performance can, however, be affected if the insulation is walked on, repeatedly disturbed, removed during electrical work or damaged by a serious roof leak.
Properly installed cellulose insulation is intended to remain in place as a long-term part of the building.
Its useful life depends on the condition of the roof and ceiling. Persistent water leaks, pest contamination, repeated disturbance and unauthorised removal can reduce its effectiveness. If tradespeople move the insulation to reach wiring or other services, the material should be redistributed to its original depth when the work is complete.
Thermguard advertises a lifetime guarantee, subject to its applicable terms and conditions. The installer should provide the warranty conditions in writing before work begins.
Thermguard is made predominantly from recycled newsprint that might otherwise have entered the waste stream. Its manufacturing process is comparatively simple, and Thermguard states that no water is used during manufacture.
The environmental benefit is twofold: recycled material is used to create the insulation, and the installed product can reduce the energy required to heat and cool a building. Environmental claims should nevertheless be supported by the current product documentation rather than broad claims such as “completely green” or “zero impact”.
Yes. Cellulose fibre absorbs sound and can help reduce noise entering through the roof or travelling between rooms through the roof space.
The improvement will depend on the roof construction, ceiling type, installation depth, gaps, windows and the source and frequency of the noise. Thermguard should therefore be described as sound-absorbing, not as a complete soundproofing system.
Thermguard publishes a noise reduction coefficient of 0.80–0.90 when installed at depths of 100 mm or more. This indicates sound absorption by the material; it does not guarantee a fixed reduction in noise throughout every home.
Thermguard is treated with fire-retardant additives and will not burn. It is fire-tested under SANS 428 and classified B/B1/2. The additives last the lifetime of the building.
Blown above the ceiling, Thermguard fills every nook and cranny, creating a seamless blanket with 100% cover. Tests in the USA found cellulose creates far better "air tightness" than rolled insulation, performing on average up to 26% more efficiently — and up to 38% more efficiently in extreme climates.
An R-rating is measured under lab conditions for a perfectly fitted product with no gaps. Batts and rolls have to be cut around beams, downlights and awkward corners, and any small gap lets heat pass straight through — so the effective performance in a real roof is often lower than the number on the bag. Loose-fill cellulose is blown to form one continuous layer with no cutting and no gaps, so what's specified is much closer to what's actually delivered.
Batts and rolls sit between the joists, not over them — and timber joists conduct far more heat than the insulated gap around them, while steel joists conduct even more. That leaves regular thermal "stripes" running across the ceiling every few hundred millimetres. Because Thermguard is blown on top as one continuous blanket, it covers the joists as well as the gaps, removing those weak points entirely.
No. Thermguard is a light material spread evenly across every square metre of ceiling, supported the same way right across each joist — it's not a point load in any one spot. A roof leak or a person walking on the ceiling puts far more concentrated weight on the board than the insulation ever does.
Thermguard slows the movement of heat through the ceiling in both directions.
In summer, it reduces the rate at which heat from the roof enters the rooms below. In winter, it reduces the rate at which warmth generated inside the house escapes into the roof space. This generally creates more stable indoor temperatures and reduces sharp temperature changes.
The exact improvement varies according to the roof, windows, shading, air leakage, orientation, local weather and existing insulation. For this reason, Thermguard should not promise a universal temperature reduction such as 6°C or 8°C.
Yes. Thermguard will drastically reduce your electricity bills for heating and cooling your home. Depending on the design of your home, the insulation is estimated to pay for itself within 2–3 years.
The actual saving cannot be guaranteed. It depends on the size and efficiency of the home, existing insulation, electricity tariffs, appliance efficiency, thermostat settings and how occupants use the building.
In most cases, yes.
Improving the ceiling insulation first reduces the amount of heat entering or leaving the home. This may affect the size of the air-conditioning system required and can reduce how hard the system needs to work.
Air-conditioning should still be sized by a qualified specialist who considers room volume, windows, orientation, occupancy and other heat loads. Insulation improves the building envelope; it does not replace correct air-conditioner design.
Ceiling insulation addresses heat transfer through the ceiling, but it cannot correct every source of discomfort.
A problem room may also be affected by:
The installer should check that the insulation layer is continuous above the affected room before recommending additional work.
R-value measures resistance to heat flow. The higher the R-value, the greater the resistance offered by the material or building assembly.
For a specific insulation material, R-value is influenced by its thermal conductivity and installed thickness. Thermguard publishes a thermal conductivity of 0.040 W/(m·K). Its published table shows an insulation R-value of approximately 2.50 at 100 mm and 3.38 at 135 mm.
The R-value of the insulation product is not necessarily the same as the total R-value of the complete roof assembly.
The required specification depends on the building’s energy zone and the total thermal performance of the complete roof assembly.
The current SANS 10400-XA:2021 framework uses energy zones rather than the original six climate zones. Current industry guidance based on the standard shows a minimum total roof-assembly R-value of 3.7 for energy zones 1–7 and 2.7 for zone 5H.
Generic deemed-to-satisfy tables commonly indicate approximately 135 mm of loose-fill cellulose for most energy zones and approximately 100 mm in 5H. These are not universal quotation figures. The roof covering, ceiling, reflective layer and other components may alter the insulation contribution required.
Adding insulation increases thermal resistance, but the benefit becomes progressively smaller once the appropriate target has been reached.
Installing substantially more than required can waste money and may make access to wiring, junction boxes or other roof services more difficult. Excess material must also not interfere with downlights, ventilation openings or equipment.
The objective is not to install the deepest possible layer. It is to install the correct, continuous and verifiable thickness for the building and energy zone.
Depth markers or another measurable reference should be used in the roof space. The installer should record the completed depth and provide photographs where practical, particularly around difficult-to-see areas.
Reflective foil works by reflecting radiant heat, but only if it faces a clear, dust-free air gap of roughly 25mm. Squashed flat, covered in dust, or in direct contact with another surface, its performance drops off sharply — in practice, close to zero. Cellulose is a mass insulator: it doesn't need an air gap to work, because it physically slows heat moving through it rather than reflecting it.
Yes. Blown cellulose is well suited to retrofit installations because it is applied through a hose into the roof space.
The installer must first assess access, roof condition, ceiling strength, existing insulation, electrical services, downlights, geysers and any signs of moisture or pest activity. The roof does not necessarily need to be replaced or the ceiling removed.
Sometimes.
Existing insulation can remain when it is dry, clean, correctly positioned and free of serious pest, mould or fire damage. Thermguard can then be used to improve coverage or increase the total R-value.
The existing material should be removed where it is:
An installer should inspect the roof before deciding whether to top up or remove the existing material.
It can be installed in many flat and low-pitched roofs, but the installation method depends on access and construction.
Where there is insufficient internal access, sections of roof sheeting or tiles may need to be lifted so the hose can be positioned correctly. The roof must then be reinstated and weatherproofed by a competent person.
No installer should promise that every flat roof can be insulated without first inspecting the roof profile, ceiling cavity, waterproofing and access points.
Thermguard can be installed above ceilings beneath both tiled and metal roof coverings.
The roof type affects heat exposure, condensation risk, access and the contribution of other roof materials to the total R-value. Metal roofs may require particular attention to condensation control and existing underlays. Tiled roofs may offer easier access by temporarily lifting selected tiles.
The product depth must still be based on the complete roof assembly and current energy-zone requirements.
Usually, but the roof space must be inspected first.
Solar panels mounted above the roof do not automatically prevent ceiling insulation from being installed. However, their electrical cabling, isolators and roof penetrations must remain identifiable and accessible.
The installer must also maintain access around geysers, valves, drip trays, junction boxes, aerial equipment and other services. Insulation should not obstruct equipment that needs inspection, ventilation or maintenance.
Do not walk directly on loose-fill insulation or the ceiling.
Walking through the insulation compresses and displaces the material, reducing its depth and potentially damaging the ceiling. Storage can also create uninsulated areas and make electrical services difficult to reach.
Where roof storage is required, a properly designed raised platform should be installed above the insulation without compressing it. Safe access boards should be supported by the roof structure, not by the ceiling board.
Bags of Thermguard are emptied into a blowing machine, which separates and aerates the fibres. The material travels through a hose into the roof space, where an installer distributes it evenly across the ceiling to the specified depth.
The installer must work around roof trusses, services and other obstructions while maintaining a continuous layer. Downlights, junction boxes, geysers and access routes must be treated correctly rather than simply buried.
Thermguard states that it uses a countrywide network of approved installers trained to apply the product according to its requirements.
A typical accessible home may be completed in approximately three hours, but this should be presented as an estimate.
Installation time depends on:
The installer should confirm the likely duration after inspecting the property.
The blowing process can create some temporary dust in the roof space. Small amounts may enter the living area through the trapdoor, ceiling gaps or poorly sealed cornices.
The installer should protect the immediate work area, manage the hose carefully and clean any dust that enters the home. Occupants who are especially sensitive to dust should avoid the work area while installation is underway.
The team will require suitable access to the property, roof or trapdoor, electricity for the equipment and space for the installation vehicle and hose.
A proper quotation should consider more than the floor area.
It should specify:
Thermguard notes that pipe lagging may be charged separately, so this should be clearly itemised rather than added unexpectedly.
The performance of ceiling insulation depends heavily on installation quality.
An approved installer should understand:
The quotation should identify the installing business and state that genuine Thermguard will be used. Thermguard publishes a national list of approved installers.
The homeowner should request:
These records are valuable because most homeowners cannot safely inspect the entire ceiling themselves.
Thermguard advertises a lifetime guarantee, but the published website wording includes an asterisk and does not set out all conditions on the product-information page.
The FAQ should therefore not say simply “guaranteed for life” without explaining:
The written warranty terms should be supplied before installation.
Flat roofs are a Thermguard specialty — in fact, many installers of insulation rolls pass these enquiries on to us. This is because Thermguard can be installed in most flat roofs without removing the roof sheets completely: the sheets are partly lifted, the insulation is blown in underneath, and the sheets are refitted.
Thermguard is treated with fire-retardant additives to improve its behaviour when exposed to heat or flame.
The technically accurate claim is that Thermguard is fire-retardant and does not support flame spread under its tested classifications. Thermguard states that it has been tested using SANS 10177 Part 5 and Part 10 protocols and is classified B/B1/2 under SANS 428 and B-S2,d0 under SANS 53501-1.
It should not be described simply as non-combustible or as incapable of being affected by fire.
No. Thermguard contractors fit protective sleeves above downlighters, isolating them from the insulation. Correct treatment of downlighters is an important part of our professional installation
Different light fittings have different clearance, ventilation and covering requirements. The installer must follow the fitting manufacturer’s instructions and applicable electrical requirements. Suitable covers, barriers or clearances should be used where required.
No damage will be done to any wires found in the roof, as Thermguard is non-corrosive. Because it's a loose-fill insulation, wiring can still easily be traced should maintenance be required.
Thermguard is installed around electrical services, but the installer must not compromise their safe operation or future accessibility.
Junction boxes, transformers, isolators and other equipment that require access should remain identifiable. Wiring should be inspected for visible damage before it is covered, and any concern should be referred to a qualified electrician.
Because Thermguard is loose fill, it can be moved locally for future electrical work. The material must be returned to the correct depth when the work is finished.
Thermguard describes its product as non-allergenic, non-toxic and non-irritant. It is installed above the ceiling rather than in the occupied room.
Installation may nevertheless produce temporary dust. Sensitive occupants, young children and pets should be kept away from the immediate work area until the installation and cleaning are complete.
Health wording should be supported by the current safety data sheet and should not imply that no person could ever experience sensitivity.
Thermguard is treated with inorganic salts that make the material unattractive or irritating to many insects and rodents. The appropriate description is insect- and rodent-repellent.
It is not a physical barrier and cannot stop rodents entering through damaged roofs, open eaves or other access points. Existing infestations should be treated, entry points should be sealed and damaged wiring should be inspected before insulation is installed.
Ceiling insulation can reduce cold ceiling surfaces and temperature differences that contribute to condensation. Continuous coverage may therefore help reduce some mould risks.
It cannot fix:
The moisture source should always be identified and corrected. Insulation should be part of the solution, not presented as a mould treatment.
Thermguard is manufactured from recycled newsprint, which is fairly absorbent. Small drip leaks won't harm the insulation or ceiling — they're absorbed by the insulation, and the moisture evaporates out the next day as the roof space heats up. This is why Thermguard is known as the "breathing insulation." Roof leaks should of course still be repaired. In the event of a major water event, such as a burst geyser, the insulation will be damaged — this is normally covered under household insurance and can be repaired by a Thermguard contractor while the geyser is being attended to.
Ceiling mould often forms on the cold patches where insulation is missing or gapped — warm, moist household air condenses on that cooler spot. A continuous, full-contact layer of cellulose removes those cold bridges, which is usually what stops the mould coming back.
Batts and rolls are pre-cut products that must be fitted between and around roof framing, wiring and other obstructions. Their performance depends on accurate cutting and close-fitting installation.
Thermguard is blown into place and can form a more continuous layer around irregular spaces and over many ceiling joists. This can reduce gaps and thermal weak points.
The comparison should be made using:
Thermguard should not claim that all batts perform poorly or that cellulose automatically makes a building airtight.
Thermguard and reflective foil perform different functions.
Thermguard is bulk insulation that slows conducted heat flow by trapping air within its fibres. Reflective foil reduces radiant heat transfer and relies on an adjacent air space to achieve its stated R-value.
A reflective layer may contribute to the total roof-assembly R-value, but only when it is installed in the correct configuration. Current SANS 10400-XA guidance requires the complete roof assembly to be assessed.
Thermguard can be used in a roof that already contains suitable foil or sisalation. The installer must account for the foil’s verified contribution rather than assuming a generic value.
Thermguard and spray foam are fundamentally different insulation systems.
Thermguard is loose-fill cellulose installed on the ceiling plane. It does not permanently bond to the roof covering or roof structure and can be moved locally when access to services is required.
Spray foam is normally applied directly to a surface or into a cavity and becomes part of that roof or wall assembly. Its suitability depends on the foam type, roof construction, moisture design, ventilation strategy and installation quality.
Generally: clear access to the roof trapdoor, make sure the installation team has power access if needed, and point out any downlights or fittings you're aware of in advance. Your installer will confirm the specifics when the job is booked.
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Our team is ready to help with questions about Thermguard, ceiling insulation, installation or quotations.
Thermguard is South Africa’s original cellulose fibre insulation, helping homes, offices and commercial buildings stay warmer in winter and cooler in summer since 1984.
Made from 80% recycled newsprint, Thermguard is blown into the ceiling to fill gaps and hard-to-reach spaces for consistent thermal coverage. Through our nationwide network of approved contractors, we provide a proven, energy-efficient insulation solution across South Africa.
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