How Commercial Roof Refurbishment Can Improve Energy Efficiency

Energy efficiency is an important consideration when councils, housing providers and commercial property owners plan major roofing works. An ageing roof may still appear serviceable from the outside while containing inadequate, damaged or saturated insulation that reduces its thermal performance.

A properly designed roof refurbishment provides an opportunity to improve insulation, address weak junctions and create a more effective roofing build-up while renewing the waterproofing system.

Premier Roofing & Construction Limited delivers commercial and public-sector roofing projects across London, Essex, Kent and the South East, including work on occupied housing, schools, public buildings and commercial properties.

How Roofing Affects Energy Efficiency

The roof forms an important part of a building’s thermal envelope. Its construction influences how easily heat passes between the occupied space and the outside environment.

An inefficient roof can contribute to:

• Unnecessary heat loss

• Inconsistent internal temperatures

• Increased heating demand

• Cold internal surfaces

• Condensation risks

• Poor occupant comfort

• Higher long-term operating costs

Roofing performance depends on more than the visible waterproof covering. Insulation, vapour control, thermal continuity, ventilation and moisture levels within the existing build-up must all be considered.

Common Problems Within Older Roofs

Older commercial and residential buildings may contain relatively little insulation compared with modern requirements. Existing insulation can also be compressed, poorly fitted or interrupted around roof details.

Common problems include:

• Inadequate insulation thickness

• Gaps between insulation boards

• Thermal bridging at edges, upstands and penetrations

• Wet or saturated insulation

• Damaged vapour-control layers

• Poorly ventilated cold-roof voids

• Insulation displaced during previous repairs

• Multiple roof coverings installed without reviewing the complete build-up

Adding new waterproofing over these problems does not automatically improve the roof’s energy performance. The existing construction must first be understood so that the proposed system addresses both waterproofing and thermal requirements.

Why Wet Insulation Matters

Insulation is designed to trap air and restrict heat transfer. When it becomes saturated, its ability to perform can be significantly reduced.

Moisture may enter the roof through failed waterproofing, defective outlets, poorly sealed penetrations or condensation within the roof build-up. The damage is not always visible from the surface.

If isolated wet areas are discovered, it may be possible to remove and replace the affected insulation. Where moisture is widespread, a more substantial strip-up or refurbishment may be required.

The correct approach depends on the roof’s construction, the extent of the moisture and whether the remaining materials are suitable for retention.

Warm Roof Refurbishment

A warm roof places the main insulation layer above the structural roof deck, beneath the waterproofing system. This helps maintain a more consistent temperature across the deck and can reduce the condensation risks associated with some cold-roof arrangements.

Warm-roof refurbishment is widely used on commercial buildings, apartment blocks and public-sector properties because the insulation and waterproofing can normally be upgraded externally.

Potential benefits include:

• Improved thermal continuity

• Reduced heat transfer through the roof

• Better protection for the structural deck

• An opportunity to improve drainage falls

• Compatibility with modern waterproofing systems

• Limited need for work within occupied rooms

Our guide to warm roofs and cold roofs explains the main differences between the two constructions.

When Insulation May Need to Be Upgraded

Major roofing work can involve requirements under Part L of the Building Regulations, which addresses the conservation of fuel and power.

The applicable requirements depend on the building, the extent of the work and the regulatory standards applying to the particular project. The proposed build-up should therefore be agreed with the client’s professional team, system manufacturer and building control where required.

It is sensible to consider insulation while the roof is already being refurbished. Upgrading it later could require the completed waterproofing system to be disturbed or replaced again.

However, the thickest available insulation is not automatically the correct solution. Designers must also consider:

• Existing and proposed roof levels

• Door and access thresholds

• Parapet and upstand heights

• Rainwater outlet positions

• Rooflights and service penetrations

• Structural loading

• Fire performance

• Condensation risk

• Interfaces with adjoining walls and roofs

The insulation must form part of a complete, properly designed roofing system.

Reducing Thermal Bridging

Thermal bridges occur where heat can pass more easily through a particular part of the construction. On roofs, these weaknesses commonly occur around:

• Roof perimeters

• Parapets

• Upstands

• Rooflights

• Plant supports

• Ducts and pipework

• Drainage outlets

• Changes in roof level

• Junctions with walls and cladding

These areas require careful detailing. A roof may contain high-performance insulation across its main area but still underperform if continuity is lost around numerous penetrations and junctions.

This is particularly relevant on plant roofs, where air-handling units, cables, ducts and pipework can make both insulation and waterproofing more complicated.

Improving Drainage as Part of the Work

Energy efficiency should not be considered separately from waterproofing and drainage.

Standing water, defective outlets and poor falls can increase the risk of water entering the roof build-up and damaging the insulation. If the underlying drainage problem is not corrected, newly installed materials may be placed at risk.

A refurbishment project can provide an opportunity to introduce tapered insulation, improve falls and replace unsuitable rainwater outlets. This helps protect the thermal layer as well as the waterproofing system.

At Buckley Court in London, we installed a new waterproofing system with tapered insulation laid to improved falls. New rainwater outlets were also fitted before the existing green roof was reinstated.

Energy Improvements on Occupied Buildings

Many councils and housing providers need to improve their properties while residents, staff or building users remain in place.

External roofing work can often be completed with limited internal access, but disruption still needs to be carefully managed. The project plan should consider:

• Scaffolding and safe access

• Noise and working hours

• Temporary weather protection

• Resident and occupant communication

• Material storage and lifting

• Maintaining entrances and escape routes

• Coordination around roof-mounted equipment

• Phased working across larger estates

At Stamford Hill Estate, PRC installed approximately 1,500m² of Bauder warm roofing across six occupied residential buildings. The project improved waterproofing and thermal performance while residents remained safely in their homes.

Roofing Projects That Combine Waterproofing and Insulation

Energy improvements are most effective when they are incorporated into a properly coordinated refurbishment rather than treated as an isolated addition.

At St Angela’s Ursuline School, the existing main-hall roof had minimal insulation and was experiencing water ingress. The completed refurbishment provided new insulation and waterproofing while converting the roof into a modern rooftop sports area.

Our Albert Dock project also included an insulated warm-roof build-up as part of the installation of a new Langley waterproofing system. This provided a long-term solution suited to the building’s exposed riverside location.

These projects demonstrate how waterproofing, insulation, drainage and the intended use of the roof need to be considered together.

Choosing the Right Roofing System

No single roofing system is suitable for every building. The selection should reflect:

• Existing roof construction

• Required thermal performance

• Roof size and complexity

• Number of penetrations

• Fire-performance requirements

• Drainage arrangement

• Access and occupancy

• Expected service life

• Maintenance requirements

• Manufacturer warranty provisions

PRC installs systems from established roofing manufacturers, allowing an appropriate specification to be developed for different commercial and public-sector buildings.

Repair, Overlay or Full Refurbishment?

Improving energy efficiency does not always require every part of the existing roof to be removed.

An overlay may be possible when the existing construction is sufficiently dry, stable and suitable for retention. Localised replacement may be appropriate where deterioration is restricted to clearly defined areas.

Full refurbishment is more likely to be required where:

• Insulation is extensively saturated

• The existing waterproofing has reached the end of its serviceable life

• Drainage needs substantial alteration

• The roof build-up cannot achieve the required performance

• The substrate has deteriorated

• Previous overlays have created unsuitable levels or detailing

The chosen approach should provide a coherent long-term solution rather than simply concealing existing defects.

Planning an Energy-Efficient Roof Refurbishment

The most effective time to consider thermal performance is during the early planning of a roofing project. This allows insulation, drainage, waterproofing, access and associated details to be incorporated into one coordinated scope.

For councils and housing providers managing multiple buildings, roofing work can also be prioritised according to condition, operational risk and planned investment programmes.

PRC provides quotations for major flat-roof, pitched-roof and waterproofing projects across occupied housing, commercial properties and public buildings.