Seminar: A Self Builder’s Guide to Ireland’s Best Performing Thermal Block

15th November 2021

During Selfbuild Live Belfast, while Self Build With Mannok exhibited at the show which attracts self-builders from the length and breadth of the country, Mannok’s Technical & Product Specification Manager, Jason Martin, took to the seminar stage. Throughout the seminar, Jason gave an in-depth presentation explaining to an audience of self-builders why Mannok’s Aircrete Thermal Block is Ireland’s best block for combined thermal, structural and fire performance!

Jason kicked of his presentation by explaining how important it is to fully consider the several types of construction available for the floors, walls, and roof of a new home, and suggested particular attention should be given to the wall construction. Jason stated, “up to 35% of heat from a building is lost through the walls which is the largest source of elemental heat loss from a home, so making the correct choice for the wall construction is very, very important.” “As well as adding that comfort factor, using the correct materials in the wall construction can save significant sums of money over the lifetime of the building, through reduced heating bills” he added.

Jason went on to introduce Aircrete by Mannok, a thermal block with impressive, structural, fire and sustainability credentials. “It’s an Autoclaved Aerated Concrete Block, with a unique microcellular structure filled with millions of tiny pockets of air which gives the block its light weight and insulating properties, yet doesn’t compromise the compressive strength in any way, in fact, it’s the same strength of a typical concrete block!”

Continuing to share more reasons why the Aircrete Thermal Block is Ireland’s best block, Jason revealed, “it’s thermal performance is exceptional, it insulates up to 10 times better than a traditional concrete block which helps self-builders achieve nZEB and Passive House standards easily, and it’s made from up to 80% recycled materials!”

After claiming that “the block really is out on its own in terms of thermal performance”, Jason went on to explain why and how self-builders can take advantage of this unique building solution to conserve heat in a home, especially during a period when energy prices are high, and everyone should be doing their part to build as sustainably as possible.

He started with thermal bridging, explaining that up to another 35% of the heat from homes is lost through thermal bridging, this is potentially another significant source of heat loss which unfortunately in most self builds, is not being properly addressed, if addressed at all. A thermal bridge occurs when a material in the building envelope with a poor thermal performance is surrounded by better performing materials, creating a path of least resistance encouraging heat from inside the home to travel through these “bridges” to the external environment.

Jason explained that thermal bridges typically occur at junctions in the building envelope where the fabric insulation doesn’t meet. Typical junctions include, floor to wall, wall to ceiling, roof abutments, around windows and doors and many more. “At these junctions, the continuity of the thermal insulation is broken, usually by a structural element such as a dense concrete block. Heat then flows out through the concrete block. Ironically, the more insulation we put in our floor, walls and roof the more heat we lose through the thermal bridge as the junction becomes easier for the heat to travel, relative to the surrounding elements.” Jason explained.

He continued to explain to self-builders that “whilst thermal bridging is an incredibly significant source of heat loss, it is simple to address. In most cases, by substituting two dense concrete blocks at the junction with two Mannok Aircrete Thermal Blocks, it will provide continuity of insulation across the junction therefore significantly increasing the thermal resistance and reducing the heat loss through the junction. This simple change can reduce heat loss through a junction ten times and there is no issue with structural performance.”

As the audience of self-builders became more confident in their understanding of the benefits of the Aircrete Thermal Block and how it prevents thermal bridging, they were very reassured to learn that mould growth, a common occurrence in homes where thermal bridging has not been addressed, can be eliminated by the correct use of Mannok Aircrete Thermal Blocks. “Reducing heat loss and saving money is a key benefit here but eliminating mould growth and living in a comfortable and healthy environment is equally, if not more important” Jason explained.

As Jason talked through several simple examples the audience began to wonder, just how many thermal bridging junctions are in a common house. Jason confirmed, “you’re typically looking at 6 to 7 junctions maybe more in some houses where you will have to introduce Mannok Aircrete blocks in order to fully address bridging in the house build.”

At this stage, Jason presented an image of a typical family home where all potential thermal bridges were highlighted. It was very evident that there was potential for heat loss in many areas of the building fabric and the image made it easier to understand why up to 35% of heat from the building could be lost through this phenomenon. It was equally evident however that to fully address the problem and introduce Aircrete at all these locations could cause some friction with the blocklayer and self-builder! The blocklayer, could ask, do I need to build the blocks here, or why do I not need to put them there?

As these conversations with their blocklayer anxiously swirled around the heads of the self-builders in the audience, Jason presented them with a solution to avoid such conversations. “What we are finding is people, who are serious about thermal bridging and looking to address ‘all’ thermal bridges, are going a small step further and building the entire leaf of their cavity wall with Aircrete Thermal Blocks. They are addressing all their thermal bridges by default and at the same time improving the overall U-Value of their wall, which is an added bonus.”

Jason added that in addition to the reduction in heat loss through addressing the thermal bridges and improving the U-value of the wall, as well as eliminating mould growth, Self Build With Mannok’s Aicrete Inner Leaf solution provides faster heating response time when compared to standard dense concrete blocks. He said, “if you come home in the evening to a cold house and switch on your heating, a dense block wall will absorb some of the heat resulting in a delay in the room reaching the desired temperature. The insulating properties of Aircrete blocks mean they don’t absorb this heat as quickly resulting in a more rapid heating response.”

On the other hand, Jason revealed that a certain amount of thermal mass in your walls is particularly important to capture and store energy from south facing glazing, which reduces the risk of overheating during the day and keeps the home warm for longer at night as the stored heat is released back into the room as it cools. Jason also suggested, as Aircrete Inner Leaf has an optimal thermal mass this is one of the main reasons it should be considered over lighter forms of construction such as timber frame or light steel frame.

Finishing of his informative seminar, Jason introduced a contemporary method of home building which takes thermal performance “one step further,” the Super Insulated Masonry Solution (SIMS), SIMS by Mannok. A singular inner leaf of Aircrete Thermal Blocks externally finished with a certified external insulation system on the outside. “Ireland has around 16 suppliers of certified external insulation system, so there’s a wide choice. This is how houses are built in mainland Europe, for example, in Germany, Poland and Austria. It is a straightforward method of construction, up to 60% faster to build, addresses thermal bridging and has a superior fire performance.”