ᐅ Insulating glass blocks with a secondary glazing panel

Hello,

I am currently in the process of buying a house that is a bit older, which I actually like for that reason, and I want to preserve its appearance as much as possible while improving the very poor energy efficiency (269.3 kWh/(m2·a)) as much as I can.

One challenge is the uninsulated extension with two glass block panels (approximately 250cm (98 inches) x 300cm (118 inches) and 80cm (31 inches) x 230cm (91 inches)). The blocks are narrower than the surrounding wall (24cm (9.5 inches), aerated concrete) and are flush with the interior side, leaving an approximately 6cm (2.4 inches) wide continuous gap on the outside.

My idea is to attach small wooden battens (2cm (0.8 inches) thick) all around to the exterior wall as a fixing point and spacer, then install one or more glass or acrylic sheets, and finally add another 2cm (0.8 inches) batten as a frame.

This would minimally affect the appearance, but would I achieve better insulation with this approach, or could it cause problems in the long run?

Thanks

Hans-Joerg

What is the purpose of the glass blocks? Why not simply replace them with "regular" windows (fixed glazing)?

hansvas schrieb:

My idea would be to drill small wooden battens around the outside of the wall as a stop/spacer (2 cm (0.8 inch) battens), then insert one or more glass or acrylic sheets, and finally attach another 2 cm (0.8 inch) batten as a frame.

This probably offers zero energy efficiency benefit.

nordanney schrieb:

What is the purpose of the glass blocks?

To let light through.

Why not just replace them with "regular" windows (fixed glazing)?

We like the appearance—there is no other reason.

It probably has zero energy benefit.

The outer pane creates an insulating air layer, basically similar to older double-glazed windows that had just normal air between the panes. It’s clear that this is less efficient than modern insulating glazing, but I can’t imagine it having no effect at all.

I am a bit concerned that moisture might condense between the panes since the surrounding masonry is capillary-active.

Hans Joerg

@hansvas
Extension, old, high energy consumption,
the windows alone are not the issue,
there is no insulation in the ceiling,
floor, walls, and doors are without insulation,
first get a clear picture of the current condition of the house, then work with an energy consultant to create a plan including the costs of each measure, and then a plan for implementation—you are groping in the dark.
Regards, Nida
PS: Double-glazed windows are never completely airtight; they allow some dry ventilation.

Nida35a schrieb:

Extension, old,

The extension is the part that is relatively new (around 1968), the rest is old (around 1850)

high energy consumption, the windows alone are not the issue,

Of course not

, the glass blocks are just one of many problems when it comes to energy consumption.

first get a clear picture of the current condition of the house,

Apart from the energy consumption, there are no problems with this house. The building condition is really good, and during the second inspection I had a building surveyor with me. But even he said that (with my priorities) it will be difficult to achieve a good energy refurbishment.

I could carry out a number of individual measures * to improve the situation, but the big leap (energetically speaking) probably wouldn’t happen. He didn’t say much about the glass blocks, which is why I brought it up here.

This is less due to the building fabric and more to the external circumstances. The old building (1850) is made of basalt stone or basalt lava, unplastered on the outside, which I like very much and for that reason I do not want to insulate it from the outside.

The extension is made of aerated concrete (including the mentioned glass blocks) and is built into a hillside, so that basically the entire ground floor extends into the slope on two sides and on one side it is connected to the garage. External insulation is difficult to implement here for obvious reasons, especially since there is another house further up the hill, so excavating the slope to get to the outer wall is not easily done.

The first floor of the extension protrudes into the hillside on one side, the other two sides are surrounded by a prefabricated, enclosed sunroom.

cu Ha-Joe

* He suggests (not a complete list, written from memory)

* replacing the windows
* replacing the old exterior roller shutters with motorized ones if possible, closing passages for strap belts etc. at the same time
* eventually reroofing the house (already planned) and adding external insulation in addition to the existing internal insulation
* if I definitely do not want to insulate the old house from the outside (which he recommends), I should have a vapor-permeable internal insulation installed, but not more than 3-4 cm (1-1.5 inches) thick. In his opinion, I should carefully look for someone who really knows how to do this well – he was noticeably skeptical. In any case, I should first determine the water vapor diffusion coefficient of the unplastered basalt walls and then contact him again before adding insulation. He seems particularly concerned about this part.
* if internal insulation is used, wall heating would be beneficial or improve the situation (I realized I didn’t ask which situation he meant, I will when I contact him again)
* if I add internal insulation, installing one or two ventilation units would also probably not be a bad idea
* the fully exposed sides of the extension should be insulated from the outside, while I should observe the other sides for a year or two to see if the walls stay completely dry.

hansvas schrieb:

We like the look – otherwise, there’s no other reason.

I honestly can’t imagine someone choosing it purely for the look without adding battens. But well, as a missionary I don’t really get BDSM.

hansvas schrieb:

The added pane creates an insulating air gap, basically like the older double-glazed windows where there was just “normal” air between the panes. It’s clear that this isn’t as efficient as modern insulated glazing, but I can’t imagine it having no effect at all.

The “normal” air has since been replaced by a special gas that prevents condensation droplets from forming; and this gas fill is tightly sealed, which the battens won’t achieve.

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