How should insulation be planned as part of a home improvement project?

Insulation works best when it is considered as part of the wider project, not added as an afterthought.
 

If a home is being extended, rewired, replastered, renovated or fitted with new heating, that can be the ideal time to improve insulation.

Walls may already be open, floors may be accessible and pipework or cables can be moved before finishes are completed.

 

Combine insulation with renovation work

Good opportunities to improve insulation include:
 

• full house refurbishments;

• room-by-room renovations;

• kitchen extensions;

• garage conversions;

• loft conversions;

• new heating systems;

• rewiring projects;

• replastering;

• window replacement;

• roof repairs;

• external render replacement;

• floor replacement.
   

For example, if a room is already being rewired, the electrician may be chasing walls and moving sockets. That can be a good time to consider internal wall insulation because sockets, cables and radiator positions can be coordinated before plastering.
 

If an external wall needs new render, external insulation may be worth considering at the same time, because some of the access and finishing work may already be required.

 

Avoid ugly or poorly coordinated details

Insulation can cause awkward details if it is not planned properly.
 

Common problems include:
 

• deep window reveals that are not insulated;

• cold bridges around floors and ceilings;

• sockets left in awkward positions;

• radiators badly refitted;

• skirting boards not aligned;

• door linings needing alteration;

• pipework left exposed;

• rooms becoming too small;

• condensation behind insulation;

• blocked ventilation;

• exterior walls looking bulky or badly detailed.
   

A good insulation job should improve comfort without making the room look badly altered.

 

Think about ventilation

As homes become better insulated and more airtight, ventilation becomes more important.
 

Insulation can help keep heat in, but moisture from cooking, washing, breathing, drying clothes and bathrooms still needs to escape. If ventilation is poor, insulation can make condensation problems more obvious.
 

Ventilation may involve:
 

• extractor fans;

• background ventilation;

• trickle vents;

• openable windows;

• ventilation gaps at eaves;

• mechanical ventilation in bathrooms, kitchens and utility rooms;

• avoiding blocked air bricks where they are needed.
   

The goal is not to make the house draughty. The goal is controlled ventilation.

 

Think about the whole house

Insulation should be considered alongside:
 

• heating system design;

• boiler or heat pump choice;

• radiator sizing;

• heating controls;

• ventilation;

• windows and doors;

• floors;

• roof condition;

• damp issues;

• room use;

• future plans.
   

A warmer wall can make a room feel much more comfortable even if the air temperature is the same. But if the heating, ventilation or moisture strategy is poor, insulation alone will not solve every problem.

 

Home Insulation Planning Checklist

Before starting insulation work, think about:
 

• whether the loft insulation is deep enough;

• whether the loft hatch is insulated and draught-proofed;

• whether eaves ventilation will remain clear;

• whether loft storage will squash the insulation;

• whether the property has cavity walls or solid walls;

• whether cavity wall insulation is suitable;

• whether external wall insulation would change the appearance;

• whether the property is listed or in a conservation area;

• whether internal wall insulation would reduce room sizes too much;

• whether a 50mm insulated lining is enough for the aim of the project;

• whether thicker insulation would be better;

• whether rigid PIR board, insulated plasterboard or breathable insulation is most suitable;

• whether the existing walls have damp problems;

• whether vapour control is needed;

• whether sockets and switches need relocating;

• whether radiators and pipework need moving;

• whether window reveals need insulating;

• whether floors, skirting and architraves will be affected;

• whether ventilation needs improving;

• whether Building Regulations apply;

• whether the work should be coordinated with rewiring, heating or plastering.
  
   

Frequently Asked Questions About Home Insulation
 

What is the best insulation to do first?

Loft insulation is often one of the best places to start because it is usually less disruptive and can make a noticeable difference. Draught-proofing and loft hatch insulation are also useful early improvements.
 

How thick should loft insulation be?

For mineral wool loft insulation, Energy Saving Trust recommends a minimum depth of 270mm. If existing insulation is thinner, it may often be topped up, provided it is dry, clean and suitable.
 

Is external wall insulation better than internal wall insulation?

External wall insulation can be very effective and does not reduce internal room size, but it changes the outside appearance and needs careful detailing. Internal wall insulation avoids changing the outside but reduces room size and needs careful moisture control.
 

Can I insulate the inside of external walls?

Yes, internal wall insulation can be added to the inside of external walls, but the build-up must be designed properly. Damp, vapour control, thermal bridging, sockets, radiators, reveals and ventilation all need to be considered.
 

Is a 50mm insulated stud wall worth doing?

A 50mm insulated lining to cold external walls can improve comfort, especially in rooms being refurbished. However, it may not achieve the same performance as thicker insulation, and it must be detailed properly to avoid condensation or cold bridging.
 

Can I use Celotex-style rigid insulation internally?

Rigid PIR insulation boards are commonly used in many building projects, but the correct thickness, fire safety, vapour control, fixing method and plasterboard finish need to be considered. The suitability depends on the wall and the room.
 

Does insulation need Building Regulations approval?

Building Regulations may apply when upgrading thermal elements such as walls, roofs and floors. The exact position depends on the work being carried out and the property. Homeowners should check before starting significant insulation upgrades.
 

Does insulation need planning permission?

Planning permission is not normally required for insulation where there is no change to external appearance. External wall insulation, listed buildings, conservation areas and Article 4 areas may need extra checks.
 

Can insulation cause damp?

Insulation can contribute to damp or condensation problems if it is badly designed or installed. This is especially important with internal wall insulation, poor ventilation, existing damp walls or older solid-wall properties.
 

Should old houses use breathable insulation?

Older solid-wall and period properties may need breathable insulation systems or specialist advice. Standard modern insulation materials are not always suitable for every older building.
 

Should I insulate before replacing the heating system?

If possible, insulation should be considered before or alongside a heating upgrade. A better insulated home may need less heat, which can affect radiator sizing, boiler selection, heat pump design and heating controls.
 

Can I insulate one room at a time?

Yes, internal wall insulation can sometimes be done room by room, especially during refurbishment. However, the detailing at junctions, floors, ceilings and reveals still needs careful thought.
 

Planning Insulation Improvements?

APN Home helps homeowners understand the type of support they may need for home improvement projects, including loft insulation, internal wall insulation, external wall insulation, heating upgrades, rewiring, refurbishments, extensions and older property improvements.
 

Whether you are topping up attic insulation, considering external wall insulation, lining cold external walls with insulated studwork or improving insulation as part of a wider renovation, it is worth getting the build-up and project route clear before starting work.
 

Tell us about your project and APN Home can help you understand the next sensible step.