Aerogel Insulation

Aerogel insulation is an insulating material built around aerogel, a very light, silica-based solid whose structure is almost entirely pore space. The pores are so small that the air inside them barely moves, so heat passes through the material far less easily than through most conventional insulants. In Slovak renovation work it appears in two practical forms: thin aerogelové dosky, meaning blankets and boards that are fixed to a wall, and aerogel insulating plasters that are applied like a render. It is a specialist material. Designers reach for it when a wall needs a lot of performance in very little thickness, or when a facade must keep its original look.

What is aerogel insulation and how does it work?

Most insulation works by trapping still air in small cells. Aerogel goes one step further. Its nanostructured skeleton is extremely thin, and the gaps between the strands are so fine that air cannot circulate through them. Heat then has to cross a long, tortuous path through a solid that carries very little of it, and the result is a conductivity that sits clearly below that of mineral wool, EPS or cellulose.

Because aerogel is a porous material and not a sealed vessel, it behaves differently from a vacuum insulation panel. A VIP loses its performance once its envelope is damaged. Aerogel does not depend on a vacuum, so it can be cut and fitted on site, which is the main reason designers choose it over VIP in an existing building.

Which forms of aerogel insulation are used in buildings?

Form	Typical use	Can it be cut on site?	Points to check
Blanket (flexible, usually fibre-reinforced mat)	Interior insulation, cavities, pipe and detail work, filling awkward gaps	Yes, with knives, shears or scissors, but cutting releases dust	Dust control, coating behaviour at high temperature, fire rating
Rigid or reveal board	Window reveals, thin interior linings, junction details	Yes, with fine tools and dust extraction	Often bonded to plasterboard or magnesium board; some include an integrated vapour control layer, which the manufacturer must document
Insulating plaster or render	Heritage facades where the existing finish has to stay visually the same	Not applicable; it is applied wet in layers	Thickness of build-up, bond to the substrate, colour and texture, lower performance than blankets

Why is aerogel used at window jambs and reveals?

A window opening is where the old masonry, the new frame and the insulation all meet. The jamb is the vertical side of that opening, and in most renovations it has very little depth to spare. A thin board can fit where a conventional layer of insulation would not, without shrinking the opening.

The critical point is continuity. Insulation in the reveal only helps if it connects to the insulation on the wall and to the frame seal. If the reveal board stops short, the thermal bridge is covered rather than broken, and the cold inner surface remains the place where surface condensation and mould risk appear. The designer should check the junction with a thermal bridge calculation rather than assume a thin board solves it.

Can aerogel plaster be used on a listed building or in a heritage protection zone?

This is where aerogel plaster earns its place in Slovakia. In a pamiatková zóna, a heritage protection zone, or on a listed building, the heritage authority judges the external appearance closely. An external thermal insulation composite system, the ETICS that dominates ordinary facade work in Slovakia, changes the depth, profile and surface of the building. On a protected facade it is often not accepted at all.

An aerogel insulating plaster is applied as a mineral finish that can be tinted and textured to match the original. Published case work from Austria shows a historic building in a protected zone insulated this way without changing its outer appearance. That is evidence the approach can work, not a guarantee that a particular Slovak facade will be approved. The regional heritage office, the krajský pamiatkový úrad, decides on colour, texture and detailing, and it should see a sample and a drawing before the design is frozen.

How does aerogel compare with vacuum insulation panels and mineral wool?

The three materials solve different problems, and a renovation often uses more than one. The table below compares them on the points that matter most in an existing building.

Property	Aerogel blanket or board	Aerogel plaster	Vacuum insulation panel
Performance per millimetre	High, well above mineral wool	Lower than blankets	Highest of the three
Cutting and fitting on site	Possible, with dust control	Applied wet, no cutting	Not possible without damaging the envelope
Fit to irregular surfaces	Good for flexible blankets	Good, follows the wall	Poor, because the panel is rigid
Suitability for visible heritage facades	Limited, mainly interior or reveal use	Strong, keeps a mineral finish	Limited, mainly interior or reveal use
Cost	Higher than conventional insulation	Higher than conventional render systems	Higher than conventional insulation

Mineral wool remains the cheapest and most forgiving option for most walls. Aerogel is chosen where thinness or finish decides the matter. Aerogel plaster is also not a free substitute for a lime plaster on old masonry, so its moisture behaviour needs the same check as any other build-up.

How should aerogel be cut and handled on site?

Cutting is the practical weak point. Blankets release fine particles when bent or cut, small enough to be inhaled deeply, and workers handling the material without controls have reported respiratory irritation and dry skin. The site instructions should set these controls out before work starts.

• Cut with hand knives, ceramic knives or shears rather than power tools where the cut allows it.
• If a power tool is unavoidable, use a HEPA-filtered tool or extraction at the cut point.
• For long cutting sessions, set up a separate area with filtered ventilation and keep it closed off from occupied rooms.
• Wear the respiratory protection, gloves and eye protection specified in the product safety data sheet.
• Bag offcuts while still on site, and clean up with a HEPA vacuum rather than a brush.

What are the honest limits of aerogel insulation?

A renovation brief should state these limits before the material is specified.

• Cost. It costs more than conventional insulation, and a plaster system costs more than an ordinary render. The premium is justified only where thickness or appearance is the controlling constraint.
• Thickness against VIP. For the same thermal performance, aerogel needs more depth than a vacuum panel. Where the reveal is truly minimal, VIP may still win.
• Dust during installation. Cutting blankets is a health task, not just a trades task, and it adds time to the programme.
• Product variation. Coatings, vapour behaviour and fire ratings differ between products. The manufacturer's documentation must match the exact wall build-up.
• Performance claims. Much reveal and plaster data comes from manufacturers, so ask for test evidence.

Used in the right place, aerogel solves a problem little else can. Used everywhere, it is an expensive way to insulate.