Do make sure your whole loft floor is covered with insulation with a minimum thickness of 100mm (ideally 270mm for maximum thermal efficiency). Don't lay it right up to the edges where the sloping roof meets the outside wall (known as the eaves) – ensure there's a gap for airflow which will help to avoid condensation.
(For more on walk boards, visit our 'How to work safely in the loft' article.) Lay the first loft roll at the eaves, leaving a 25mm gap away from the eaves for ventilation to help prevent condensation.
You don't want to put your insulation right up into your eaves though, as generally there will be vents in your eaves for airflow in the loft space. Blocking those vents could cause issues further down the line. Putting it just up to the wall plate, not on top of should be fine.
Insulation that touches the rafters provides better coverage and reduces the risk of heat loss. By creating a tight seal between the loft insulation and the roof, energy efficiency is improved, resulting in lower energy consumption and reduced utility bills.
In addition to walls and attics, insulation should be installed in ceilings with unheated spaces, basement walls, floors above vented crawl spaces, cathedral ceilings, floors over unheated garages or porches, knee walls, and in between interior walls—especially bathrooms—as well as ceilings and floors.
Warm loft insulation (Professional)
For the full recommended depth of 270mm, insulation must be installed between and beneath the rafters. You'll also need Building Regulations approval before work can begin.
The first layer should have the facing against the drywall to act as a vapor barrier. (The general rule for insulation is that the facing always goes toward the conditioned space.) The second layer of insulation should be unfaced so that moisture doesn't collect between the layers.
It's important to leave a ventilated air gap between the insulation and the boards to prevent condensation on the underside of the boards.
While loft insulation is an effective way to improve energy efficiency and reduce heating costs, over-insulating can lead to several potential issues. Firstly, over-insulation can lead to poor ventilation in the attic, which can cause moisture buildup and increase the risk of mould growth.
Remember that a two-inch breathing space between the insulation and the roof sheathing must be included to allow for ventilation. If I leave room, it's hard to fit more than R-13 without going to rigid foam board.
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).
Before you decide to install new loft insulation, it's important to assess the condition of your existing insulation. If the insulation is still in good condition, it may not need to be removed. However, if it's damaged, damp, or infested with pests, it should be removed before installing new insulation.
You'll need to start laying with a minimum gap of 25mm between the eaves and the insulation to ensure a suitable air gap. Maintain this gap along two opposite sides of the loft.
Pushing or blowing insulation too far into the eaves or leaving it partially unrolled can obstruct cross ventilation. Cross ventilation is vital for preventing condensation.
Current government recommendations are for loft insulation thickness to achieve a depth of 270mm, but some new properties are increasing their level of loft insulation to 300mm. Again, as long as the loft has adequate ventilation, this is fine. You may lose a little storage space, but you will save money!
Insulation is often laid in contact with the roofing felt. Where the felt is impervious any contact condensation will run down the felt and make the insulation damp.
One important thing to remember is that insulation should never be pushed right into the eaves because it will interfere with airflow. If you're going for a warm loft then you'll need much more insulation to be able to cover the underside of the roof along with the gable and party walls.
Absolutely! By reducing the amount of energy needed to heat your home, loft insulation also reduces carbon emissions.
While over-insulated attics aren't as common as under-insulated attics, it is possible to put so much insulation in your attic that it has a negative impact.
Overall, the second layer of insulation plays a crucial role in improving insulation performance, reducing heat loss, and maintaining a comfortable and energy-efficient living space.
A quarter of all household heat is lost through the roof in uninsulated homes, according to the Energy Saving Trust. Spray foam is the most efficient type of insulation when it comes to keeping heat inside your loft. You could be eligible for a grant to help you with the costs of loft insulation.
It provides an additional layer of insulation by trapping air and helps to prevent moisture buildup by allowing for ventilation. So, it's always recommended to leave an air gap when installing insulation, whether it's in your walls, roof, or floors.
Never place insulation close to water heaters, oil burners or anything hot. The backing is especially flammable and will be a major fire hazard for your home.
Besides safety concerns, installation inexperience can result in insulation mistakes that can affect both the quality of your insulation and installation. Improper placement can leave gaps and cause energy loss, lessening the insulation's lifespan.
When installing faced insulation, the facing should always point toward the interior, heated, or air-conditioned space. For example: On exterior walls, the facing should touch the drywall. In attics, the facing should point down toward the ceiling below.