Building Affordable Homes to Passive Standards – Nationwide

Insulation requires high levels of air tightness in order to perform to its highest capability. This is typically explained using the “woolly jumper” analogy – imagine going on a windy winter walk wearing only a single layer woolly jumper. Wind would blow through the holes, right? Now apply a light wind breaker barrier over the single layer. This has a dramatic impact on the insulating capability of the woolly jumper as it reduces air circulation. So in order for your insulation to be most effective, it requires an air tightness barrier to protect the build against air movement on both sides.

The simple answer is no – it’s not really possible to “over-insulate” your home, in fact the more the better! However, there is always a point of diminishing returns where the insulation can cost more than the improvement in heat retention in terms of energy savings.

Insulation should be applied between any barrier that stands between cold & warm air or heated & unheated spaces. The most important areas to insulate heavily are your walls (40% of heat lost), followed by the roof (25%), windows and doors (20%) and lastly the floor. We offer an insulated foundation system & four closed timber frame wall panel options, all offering differing u-values within the passive standard range. All systems are designed specifically for optimal energy efficiency & performance.

Air tightness is essential to a comfortable, energy efficient & healthy home. On average, we spend 90% of our time indoors so it only makes sense to ensure our homes are as free from draught & cold spots as possible – especially when investing heavily on insulation. Air leakage can account for up to 50% of all heat loss in a well-insulated home. It is important to remember though that the building’s envelope is still breathable, aided by the likes of a Mechanical Heat Recovery Ventilation System (MHRV) bringing fresh warm air into your home. The air tightness barrier simply reduces air leakage to a minimum, ensuring a highly energy efficient home.

Ventilation is important in any home regardless of the level of air tightness. It’s essential that adequate fresh air circulates. Controlled ventilation through windows & doors had been suffice in older homes with poor insulation & uncontrolled air exchange through cracks & gaps in the build envelope. In fact, the leaky windows provided enough ventilation without even opening the vents! Today, with improved insulation & air tightness at the forefront of increased energy efficiency, systems such as Mechanical Heat Recovery Ventilation (MHRV) are becoming extremely popular. These things combined are essential for improved comfort, increase energy performance & a healthier, future-proofed family home.

In a timber frame structure, all areas can be sealed using an air tightness membrane & tape. It is undeniably a much easier & therefore cheaper build process than with standard masonry construction. For example, the walls in a block built home are only airtight if an internal plaster is applied straight to the block work & spread evenly at full coverage. It’s important to keep this in mind if you intend to internally insulate to increase your u-value. There is an option to externally insulate your block build, however this would mean using insulated boards as your external walls rather than block which negates it’s purpose.

Another benefit of timber frame is that your wall cavity is left completely free to do it’s job & the thermal responsiveness of timber allows the build to heat & cool quickly. With block, self-builders are having to full fill their cavity in order to achieve the minimum Part L regulations.  To achieve maximum levels of efficiency, internal or external insulation is required in a block build – both of which can cause significant problems. In comparison, timber frame benefits from a 100mm exterior leaf of block, open cavity (as it should be!) & a thermally responsive inner timber frame structure packed full with quality  insulation & a complete airtight seal.