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INSULATING YOUR HOME - YOUR CHOICES EXPLAINED. . .


When it comes to insulating your new or existing home, you’ve probably heard about plenty of different methods. But it can be overwhelming to know which type is the best for your home, so we’ve broken it down a little and explained 5 available options, with pros and cons for each.

Types of insulation for residential use

Before You Begin: Choose the Right Level of Insulation.

Before you consider the kind of insulation, you’ll want to make sure you know how much insulation you’ll need, and it’s best to start by determining what U-value is recommended for your area. U Value is measured across a complete construction (lower is better). R-values (thermal performance of each component ) are then individually added into a U-Value calculator to give for example, a wall or floor or roof construction U Value. The R Value measures insulation’s ability to resist heat travelling through it. The higher the R-Value, the better the thermal performance of the insulation and the less energy you’ll waste heating and cooling your home. R Value will typically rise with increasing the thickness of product specified.

Where Do You Need It?

You also need to consider where you need to add insulation. If it’s for a wall in a home that’s already built, you’ll most likely need to add insulation either inside the existing walls or to the outside of the walls. If it’s for an existing loft or crawl space, you may be able to use Fibreglass or Rockwool blanket or a PIR foam board insulation.

For unfinished walls, floors, and ceilings, BMD suggests the following five types of insulation because they can be built as you go or fitted between studs, joists, and beams. Here are some choices, including the pros and cons of each:

Blankets & Roll Insulation –

Blankets or rolls of insulation can be made of mineral wool, (either Glass Fibre Based or Volcanic Rock Based eg. Rockwool), plastic fibres, and natural fibres—like cotton or sheep’s wool. These types of insulation generally come without a facing, but facings made of kraft paper or foil-kraft paper are also made which can act as a vapour barrier.

Pros: Fibreglass blankets and rolls are relatively cheap, very easily available and can be installed in ceilings, unfinished floors, attic spaces, and crawl spaces. Cheap cost per m2

Cons: Fibreglass blankets and rolls have an R-value of 2.25 m2K/W per 100mm of thickness, so you may need to add 270-300mm of insulation thickness to achieve the right amount of insulation. If you’re insulating an attic or crawl space that’s already been built, you’ll need plenty of room for installation.

Polystyrene, PIR Rigid Foam or Phenolic Foam Board –

PIR Insulation Board to Loft Room

These rigid panels of insulation can be used on almost any part of the home, from the roof to the cavity walls and also the ground & first floors. They can be basic EPS 70 Polystyrene, PIR Insulation such as Celotex or Recticel, or perhaps Phenolic Foam boards such as Kingspan Kooltherm, each of which is progressively more insulating than the former. You can also get all of these types of insulation bonded to plasterboard in various thicknesses, which can save time and make the process of insulating and boarding over a lot quicker

Pros: The PIR and Phenolic boards offer much higher R-Values than other insulating materials of the same thickness, and they’re easy to work with. Medium cost per m2 for PIR

Cons: You can’t use rigid foam or foam board to insulate existing walls unless you're prepared to fit inside or outside of the external walls. Kooltherm Phenolic boards are more expensive than PIR (Celotex /Recticel) type boards but can save you thickness. Higher costs per m2 for Kooltherm & other phenolic boards.

Multi-Foil Insulations –

This type of insulation is made up of multiple layers of foam and foiled sheets - some of the foiled sheets can also encapsulate air bubbles. Generally the more layers there are in the overall thickness then the more insulating it will be. Some versions are suitable for use outside of the rafters and under battens whilst others are used internally under rafters or in floor voids. Special UF (Underfloor) versions are made for laying underneath under-floor heating installations. Typical multifoil brands would be Superfoil, Actis or Thinsulex

Pros: Easier to fit than many other insulation types, as it is a blanket it can be stapled directly over joists or in between timbers. Relatively thin for the performance it gives. Medium cost per m2.

Cons: You’ll need to remember to allow for overlaps and foil taping of the multifoil rolls at places where you are joining 2 pieces together to thoroughly air seal and also that you MUST maintain a minimum 25mm air gap either side of the sheets to allow them to "fluff up" and trap air between layers - if you try to install flat against a hard surface or another material it will not perform as intended. For example if you staple to rafters there is often an air gap behind the insulation but then you will need to cross-batten on the inside of the multifoil before applying plasterboard so that you maintain an air gap on the other side. Under-floor multifoils such as Tri-iso Sols and Superfoil SFUF are the only exception to this and can be installed directly against floor surfaces.

Insulated Plasterboard –

Also sometimes called Thermal Laminate Board, Insulated Plasterboard is available as either a Polystyrene, PIR Foam, or Phenolic Foam insulation backing, which is then bonded to a sheet of plasterboard (normally 12.5mm but can also be 9.5mm on some boards). The majority of boards can be either mechanically fixed into place with insulated plasterboard anchors, or dot and dabbed onto a solid brick or block wall using drywall adhesive. Please remember that you will still need some fixings when you are dot and dabbing boards into place so that the boards are held in place and supported until the drywall adhesive has set.

Pros: Quicker and easier to fit than 2 separate layers of insulation and plasterboard, especially to slopes and ceilings. When fitted over the insides of rafters, helps to eliminate cold spots where the timber rafters would otherwise be directly against the back of the plasterboard.

Cons: More expensive than fitting 2 separate layers of insulation and plasterboard. Only available in thinner thicknesses due to the weight of the board not easily being supported by dot and dab methods once it gets too thick and heavy. Higher cost per m2 than using separate layers of insulation and plasterboard.

Acoustic Insulation –

Acoustic Insulation normally deals with one of two issues that you need to address when you are trying to insulate for sound transmission. The first is transmission of vibrations which can be helped / reduced by using (for example) rubber matting type insulants (such as Isorubber Base) that can help to isolate one material from another so as to reduce the effect of vibration. Other methods include resilient bars (to isolate the plasterboard to a ceiling below a floor from the floor above), and joist hoods which fit over the top of each joist to isolate them from the flooring to go over that. The second issue is that of trying to absorb the airborne sound between one room and another (or one floor and another) and generally this is dealt with by the use of insulation roll or slab which is denser than normal to help absorb/dissipate sound. For stud partitions a basic method is to use Acoustic Partition Roll (approx 20 Kg/m3 density) and for more improved sound absorbency you could choose to upgrade from that to a Rockwool RWA45 or Flexi Slab (45Kg/m3), an RW3 Slab (60 Kg/m3) or even an RW5 Slab (100 Kg/m3) for increasing levels of absorbency.

Pros: Good acoustic isolation combined with sound absorbance can make a dramatic difference to the usability of the finished property.

Cons: Be aware of the increased weight of dense insulation such as acoustic slabs in your walls and especially your floors, and allow for the weight in your design. Good acoustic insulation does not always give such good thermal insulation.

For more advice on any of these options,

Alternatively visit our online store at www.directinsulation.com at any time 24 hours a day and purchase online.

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