IS IT WORTH INSULATING AN OLD HOUSE? COST - EFFECTIVE SOLUTIONS AND CONSIDERATIONS*

In the past, houses were rarely and poorly insulated, and it's interesting to note that many old houses in the UK still lack insulation today. This raises an important question when considering the purchase of such a property: is it worth insulating an old house? Additional costs should be factored in, but the overall condition of the walls, floors, and roof plays a crucial role in ensuring the water impermeability necessary for the insulation we intend to install. In this blog post, we will explore various insulation options and techniques suitable for old houses, focusing on affordability, insulation methods that don't require tearing down walls, interior insulation, considerations specific to the UK, insulating under floorboards, and insulating old stone houses.

HOW TO INSULATE AN OLD HOUSE CHEAPLY?

Insulation has never been considered a cheap investment. Many of us wonder, therefore, how to save on insulation. How and where can we buy insulation at a lower cost? And finally, is it possible to purchase insulation inexpensively?

To insulate an old house cheaply, it is crucial to start by properly sealing the house, including the walls and floorboards. Utilising a heavier layer of insulation for windproofing can reduce the overall investment costs. Therefore, various types of sealing membranes should be applied. Among the leading products in the UK market are Novia's range of products. However, there are other options available that combine insulation and provide moisture protection. One such option is Rockwool products, which are often coated with aluminium foil on one or both sides. While they may not be the cheapest option, they eliminate the need for additional membranes, thus reducing labour costs.

To insulate a house cheaply, it is advisable to:

- Thoroughly seal the house against drafts and air leaks. Proper sealing of windows, doors, and any gaps or cracks in the walls can significantly improve energy efficiency and reduce heat loss.

- Consider upgrading to double-glazed windows. Double-glazing provides better insulation and helps to retain heat inside the house. While it may require an initial investment, it can lead to long-term energy savings.

- Look for products that offer dual functionalities, combining insulation with other features that can help reduce labour costs. For example, using insulation products that also provide moisture protection or include built-in vapour barriers can save on additional material and installation expenses.

- Search for the best deals online. Many retailers and suppliers offer competitive prices and discounts on insulation materials. Comparing prices and exploring online marketplaces can help you find affordable options without compromising on quality.

CAN I PUT NEW INSULATION ON TOP OF OLD?

We have already discussed this topic in a separate article titled "SHOULD I REMOVE 80 YEARS OLD INSULATION?"
If you want to find out whether you can put new insulation on top of old insulation, please click here:  
In summary, it is generally acceptable to lay new insulation on top of old insulation when:

• The old insulation is intact and undamaged.
• The old insulation is not wet or damp.
• The old insulation has not been compromised by rodents such as mice or martens.
• The old insulation does not contain asbestos particles.
• If the old insulation is not compressed due to the presence of storage boards.
• If the old insulation is not falling apart.
• If the old insulation does not contain dust that has passed through and accumulated within it.

WHAT IS THE BEST INSULATION FOR AN OLD HOUSE?

In general, there is no specific insulation designed exclusively for old houses. However, when insulating older buildings, it is important to consider their inherent air leakage and the potential for moisture infiltration within the insulation. The best insulation options for such scenarios appear to be rockwool insulation like Rockwool RW45 or Knauf RS45. Rockwool mineral wool, in particular, provides excellent breathability for walls and floors. The use of highly impermeable insulation is not recommended for old buildings, as it may potentially harm the structure rather than help it.

When insulating the exterior walls of old houses, it is recommended to use products such as Rockwool DD. These types of insulation provide the necessary breathability for old walls that are often damaged or damp. By using Rockwool DD, you can ensure proper ventilation and prevent moisture-related issues in the walls of the building.

In summary, mineral wool, whether it's rock wool or glass wool, is considered the best choice for insulating an old building. These types of insulation provide excellent breathability, allowing moisture to escape and preventing the buildup of condensation within the walls. This breathability is crucial for maintaining the structural integrity of the old building and preventing issues like dampness and mold growth. Therefore, mineral wool insulation is recommended as it offers complete breathability for optimal performance in insulating old buildings.

WHERE SHOULD YOU NOT PUT INSULATION ON OLD HOUSE?

When it comes to insulating an old house, there are certain areas where insulation may not be suitable or can cause potential issues. Here are some key areas where insulation should be approached with caution or avoided altogether:

Exterior Brickwork
It's generally not recommended to install insulation directly against the exterior brickwork of an old house. Traditional solid brick walls are designed to breathe and allow moisture to evaporate. Adding insulation on the exterior can trap moisture, potentially leading to dampness, mould growth, and deterioration of the brickwork. Instead, consider insulating from the interior or using breathable insulation materials such as Rockwool DD.

Electrical Outlets
Insulation should not be compressed or obstruct electrical outlets, switches, or light fixtures. This can create a fire hazard and interfere with the proper functioning of electrical systems. Take care to insulate around these areas without blocking or covering them.

Vented Attics
In some older houses, attics may be designed to have ventilation to allow moisture to escape. Blocking these vents with insulation can lead to moisture buildup and potential damage to the roof structure. Insulate the attic floor instead to create a thermal barrier while maintaining proper ventilation.

Moisture Areas
Avoid installing insulation in areas prone to moisture, such as basements with ongoing water issues or areas with plumbing leaks. Insulation in these areas can become damp or damaged, promoting mould growth and compromising its effectiveness. Prioritise addressing moisture issues before considering insulation.

Remember, each old house is unique, and it's essential to assess its specific characteristics and consult with professionals to determine the most appropriate insulation approach. By avoiding these potential problem areas, you can ensure a safer and more effective insulation installation in your old house.

BREATHABLE INSULATION FOR OLD HOUSES

If you're insulating an old house, it's advisable to use highly breathable insulation products, meaning products with a structure that allows the walls to breathe. This includes all mineral wools, whether glass or rock wool. In contrast to glass wool, rock wool products like Rockwool DD have the additional advantage of self-drying capabilities. In the event of potential moisture exposure, the insulation remains usable; you just need to stop the source of water leakage, and the insulation will dry out naturally. However, this does not apply to glass wool. Its structure tends to bind fibres together, resulting in prolonged moisture retention. Over time, this can lead to mould on the walls and ultimately necessitate replacement.

Breathable insulation products for insulating old houses also have the benefit of being lightweight. This way, you avoid unnecessarily burdening the existing walls of the building.

By using breathable insulation products, you can simultaneously achieve sound insulation in your home of approximately 20-40 dB. This is significant considering that 40 dB is the noise level of a typical conversation.

Here are some commonly used products for insulating old houses:

Rockwool DD
Rockwool RWA 45
Rockwool RW3
Rockwool RW5
Knauf RS45
Knauf RS60
Knauf RS100
URSA

HOW TO INSULATE AN OLD HOUSE WITHOUT TEARING DOWN WALLS?

Tearing down walls is not always a pleasant task when renovating an old house. It is often unnecessary, especially when it comes to insulating the walls. If the wall is in a satisfactory condition to fulfil its structural requirements, all is needed is to insulate it using a highly breathable insulation material like mineral wool. This usually involves removing the plaster from both sides of the wall, allowing it to dry out before proceeding with insulation. If the wall doesn't have significant vertical cracks below the ‘thickness of a pen’, simply securing it with specialised clips or occasionally reinforcing the lintel should suffice. This method is much cheaper than demolishing and rebuilding the wall. Additionally, demolishing a wall is not always possible, especially when it's a load-bearing wall. Disturbing such a wall could lead to a structural disaster and the collapse of the building.

Most people opt to repair the existing wall and insulate it using rock wool, whether on the inside or outside.

INSULATING AN OLD HOUSE FROM THE INSIDE: A GUIDE TO BREATHABLE INSULATION

Generally speaking, the ideal method for insulating an old building is from the outside. However, there are situations where this may not be possible, especially in heritage buildings. In such cases, the only option is to insulate the walls from the inside. Fortunately, manufacturers like Rockwool offer solutions tailored for this purpose.

When constructing a stud wall for interior insulation, products like Rockwool RWA45 and RW3 can be employed. Their density, when combined with two layers of plasterboard, provides sufficient noise reduction of approximately 30 dB. But that's not all. The most important aspect is that they ensure nearly 90% breathability of the interior wall. By adhering to the minimum distance from the wall and ensuring insulation continuity, this can be achieved.

By utilising Rockwool RWA45 and RW3, you can effectively insulate the interior of your old house. This solution not only reduces noise levels but also ensures optimal breathability for the walls. Creating a stud wall with these products provides an effective barrier to sound transmission while maintaining the ability of the wall to "breathe."

It's important to note that when insulating from the inside, attention should be paid to proper installation techniques. Following manufacturer guidelines and considering factors such as moisture control and air sealing will help achieve the best results. Consulting with a professional or insulation specialist is recommended to ensure the insulation process aligns with the specific requirements of your old house.

THE BENEFITS OF INSULATING UNDER FLOORBOARDS: IS IT WORTH IT?

Insulating the area underneath floorboards is a home improvement project that offers several significant advantages. While it may require some investment of time and resources, the benefits make it a worthwhile consideration for many homeowners. Let's explore the advantages in more detail:

Insulating under floorboards helps create a thermal barrier, preventing heat loss through the floors. This is particularly beneficial in colder seasons when the temperature difference between the inside and outside of your home is more significant. By reducing heat loss, your heating system won't have to work as hard to maintain a comfortable indoor temperature, resulting in lower energy consumption and potentially reduced heating bills. Insulation under floorboards helps to create a more comfortable living environment. It provides a barrier against cold drafts, preventing the chill from permeating through the floors. By insulating, you can enjoy warmer floors and minimise the discomfort of walking on cold surfaces, especially during winter months.
Insulation not only helps with temperature regulation but also acts as a sound barrier. It can effectively reduce airborne noise transmission, such as footsteps or voices, between floors. This is particularly advantageous in multi-story homes, where noise disturbances can be bothersome. Insulating under floorboards can create a quieter and more peaceful living space.
Insulation materials designed for underfloor use often come with moisture-resistant properties. By installing appropriate insulation, you can help mitigate issues related to moisture and condensation, preventing potential damage to the floor structure and reducing the risk of mildew growth.

Insulating under floorboards can also be seen as a valuable upgrade by potential buyers if you ever decide to sell your home. Energy-efficient features and improved comfort are attractive selling points, and having insulated floors can make your property more appealing to prospective buyers.

In conclusion, insulating under floorboards offers numerous benefits, including improved energy efficiency, increased comfort, soundproofing, moisture control, and potential property value enhancement. 

INSULATING AN OLD STONE HOUSE: FINDING THE PERFECT BLEND OF PRESERVATION AND ENERGY EFFICIENCY

Insulating an old stone house requires specialised knowledge and skills. When it comes to insulating an old stone house, striking a balance between preserving its historical charm and enhancing its energy efficiency is essential. This delicate task requires thoughtful consideration and specialised approaches to ensure the integrity of the structure while maximising energy-saving potential.

Utilise breathable insulation materials
Traditional stone houses require breathable insulation to allow for moisture management. Natural materials like rock wool, cellulose, or hemp insulation can be effective options, as they allow vapour to pass through while still providing thermal insulation. These materials maintain the breathability of the stone walls, preventing the accumulation of moisture and potential damage.

Insulation techniques for stone walls
Insulating stone walls can be challenging due to their thickness and irregular surfaces. One approach is to apply an internal insulation system using insulated plasterboard such as Kingspan K118 or Xtratherm XT/TL  creating a gap between the insulation and the stone surface. 

CONCLUSION

Insulating an old stone house presents a unique set of challenges, as it requires finding the perfect balance between preserving its historical charm and enhancing its energy efficiency. By carefully assessing the condition of the stone walls, utilising breathable insulation materials, focusing on key areas, implementing specialised insulation techniques, and seeking professional expertise, homeowners can successfully achieve this delicate equilibrium.

The process of insulating an old stone house goes beyond simply improving energy efficiency. It involves respecting and honouring the architectural and historical value of the property. With the right insulation choices, such as breathable materials that allow for moisture management, homeowners can ensure the long-term preservation of their stone walls while simultaneously reducing heat loss and energy consumption.

Related articles:

SHOULD I REMOVE 80 YEARS OLD INSULATION?

A COMPREHENSIVE GUIDE TO INSULATED PLASTERBOARD FOR CEILING INSULATION

THE SOUNDPROOFING POWER OF WOOL: UNVEILING THE TOP CHOICES

STEP-BY-STEP GUIDE: HOW TO INSTALL CELOTEX BOARD BETWEEN FLOOR JOISTS

THE UGLY TRUTH ABOUT ROCKWOOL AS A SOUNDPROOFING MATERIAL?

FOIL INSULATION: TO GAP OR NOT TO GAP? THAT IS THE QUESTION!

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