Squashing your insulation reduces its effectiveness by 50% Numerous studies on the topic have indicated that there's a huge number of Britons who don't understand why doing this is so problematic. Mineral wool type insulation (the most common loft insulation) needs to retain its full depth in order to work effectively.
Wall Insulation (R-13 recommended for walls above grade)
If this is the case, the fiberglass batts may need to be compressed. Compressing home insulation doesn't render it completely ineffective. And, depending on the circumstances, lost R-value can be restored by topping off the cavity with loose-fill insulation.
Don't squash the insulation as this can reduce its thermal performance by over 50%. Don't install loft boards directly to joists or trusses. Don't remove any insulation as this can reduce the thermal performance of the loft.
It's important to leave a ventilated air gap between the insulation and the boards to prevent condensation on the underside of the boards. Make sure you don't squash the mineral wool when you fit the boards on top, as this will reduce its insulation value.
One way that excessive loft insulation can cause dampness is by blocking ventilation. Proper ventilation is necessary to allow moisture to escape from the building. If insulation is installed too thickly or packed too tightly into the loft, it can block air flow and prevent moisture from escaping.
Squashing your insulation reduces its effectiveness by 50%
Numerous studies on the topic have indicated that there's a huge number of Britons who don't understand why doing this is so problematic. Mineral wool type insulation (the most common loft insulation) needs to retain its full depth in order to work effectively.
Too much insulation will leave humidity and moisture to accumulate in your attic space. This can lead to mold growth on your walls and insulation. There might also be water damage to the support beams in your home's roof.
Should I remove old loft insulation before laying new? Older insulation material will typically need to be removed before adding new insulation. However, in some cases the material may be in good condition, meaning you can simply top up the existing insulation material for a fraction of the cost of a full replacement.
One important thing to remember is that insulation should never be pushed right into the eaves because it will interfere with airflow.
In order for insulation to do its job, sufficient airflow to the outside surfaces is required. Good ventilation in your attic will allow the moisture to get out.
Boards for loft flooring can be installed on top of insulation using plywood, wood, or plastics. Installing loft flooring and boarding over insulation helps save space, prevent heat loss, and increase home value.
For example, if it is only slightly damp then it may be an option to dry the insulation out. You can do this by using a dehumidifier in the area. Wet insulation that is thoroughly drenched and in a closed wall cavity likely won't dry out and in this case, it's better to completely replace the damaged insulation.
If your loft is not used for storage purposes, doubling the insulation layers is highly recommended. By doubling the insulation layers in your loft, you increase its R-value, which in turn reduces its U-value (lower U-value is better).
You will want to bring up your attic up to R-38:
If your attic has 5-6″ of existing insulation, you'll want to install an R-19 to achieve a total of R-38.
Install Insulation
Battens can be simply pushed into place, they should have a side with a paper facing or a vapour control layer. This side should be facing into the loft and can be stapled to the joists to hold the insulation in place.
Do not squash your insulation by placing items or boarding directly on top. If you squash your insulation, you reduce its thermal performance by up to 50%. It can also create issues in the loft such as damp and condensation as the insulation does not have sufficient airflow to be protected or work effectively.
Insulation shouldn't be laid over any electric cables. Where possible, clip them to the roof joists or gently lift them out of the way whilst you install, before laying them over the insulation when it's in position.
Should you leave a gap between the insulation and the roof? Yes, you should leave an air gap between the insulation and the roof to allow proper ventilation and prevent moisture buildup.
Loft insulation usually lasts 40 years or more if properly maintained and pays for itself many times over its lifespan. However, this greatly depends on how well it was installed and the type of material used.
Leaving Too Many Gaps
One of the biggest problems DIY homeowners face is leaving too many gaps in their insulation. Gaps or insulation that isn't secured correctly can leave the building structure open to air and moisture leaks. Spray foam insulation is best for reaching into small cracks and any areas left open.
However, due to its construction with natural materials, eventually the product will lose effectiveness. Fiberglass insulation typically needs to be replaced 15-20 years into it's life, as it can easily become dirty, wet, moldy, and ineffective if there's a roof leak or water damage of any kind.
Also, when laying down additional insulation, work from the perimeter toward the attic opening. Never lay insulation over recessed light fixtures or soffit vents. Keep all insulation at least 3 inches away from recessed "can" lights, unless they are rated IC (Insulated Ceiling).
Many of us know what causes mould; when moisture is trapped in the rooms of you home. Sometimes, there is insufficient insulation in the walls, so mould grows. However, not many people realise that additional insulation isn't always the answer. In fact, too much insulation can be the secret cause of mould.
Can I put plywood over insulation in the attic? Yes you can install plywood subflooring directly over the floor joists and insulation on your floor. You need to install rigid insulation boards on top of the attic flooring joists and then install plywood over the top.