ilias igoumenidis

Civil Engineer - Passivhaus Designer - Ecological Building Systems - Retrofit Coordinator - Passivistas - Hellenic Passive House Institute

[ilias igoumenidis @igou]

Mould needs moisture, time and a surface to grow.

#retrofit #mould #architects

[ilias igoumenidis @igou]

Wall moisture behaviour isn’t a moment in time, it’s a movie.

If your assessment only takes a snapshot, don’t act surprised when the building surprises you.

#architects #retrofit #solidwalls #iwi

[ilias igoumenidis @igou]

❓❓❓If you could ONLY afford TWO measures, which combination would you prioritise to reduce mould risk long term in your old house, and why?

❓Comment below (A,B,C or D), and if you want share your thinking.

#retrofit #mould #architects

[ilias igoumenidis @igou]

🫗🫗🫗
The 3 rules of capillary action:
𝟭:𝗧𝗵𝗲 𝗽𝗼𝗿𝗲𝘀 𝗺𝘂𝘀𝘁 𝗯𝗲 𝘃𝗲𝗿𝘆 𝘀𝗺𝗮𝗹𝗹
𝟮:𝗧𝗵𝗲 𝗽𝗼𝗿𝗲𝘀 𝗺𝘂𝘀𝘁 𝗰𝗼𝗻𝗻𝗲𝗰𝘁 𝘁𝗼 𝗲𝗮𝗰𝗵 𝗼𝘁𝗵𝗲𝗿
𝟯:𝗔𝘁 𝗵𝗶𝗴𝗵 𝗵𝘂𝗺𝗶𝗱𝗶𝘁𝘆 𝘁𝗵𝗲 𝗽𝗼𝗿𝗲𝘀 𝗺𝘂𝘀𝘁 𝗳𝗼𝗿𝗺 𝗹𝗶𝗾𝘂𝗶𝗱 𝗳𝗶𝗹𝗺𝘀

[ilias igoumenidis @igou]

🌶️🌶️🌶️
The most dangerous retrofit mistake? The right insulation with the wrong boundary condition.

Why?
You eat chilli peppers. Your internal climate changes instantly. The wall feels these changes too.

 How?
Download the 7 boundaries her:
🌶️ https://t.co/ifRzpih8O8

[ilias igoumenidis @igou]

“To gap or not to gap? this the question”

(…behind the insulation?)

Download the full guidance document here: https://t.co/k1X2f8lKDJ

#architects #retrofit #solidwalls #iwi

[ilias igoumenidis @igou]

💦💦💦
Here are a few ways moisture travels inside porous walls:

1; Vapour Diffusion
Moisture through tiny pores

2; Capillary Action
Liquid water through pore channels

3; Surface Diffusion
Micro-water film along pore surfaces

4; Air Leakage
Moist air through cracks

[ilias igoumenidis @igou]

🧂🧂🧂

Why is there rice in a salt shaker?
Without the rice, the salt gets sticky when the air is humid.
Rice is #hygroscopic; it soaks up extra moisture.

Some insulation materials do this too: they wick moisture & release it later, helping walls stay dry.
#architects #retrofit

[ilias igoumenidis @igou]

🚦🚦🚦
A paint’s breathability is like wearing T-shirts:
1x T-shirt=easy to breathe
2x T-shirts=harder
3x T-shirts=not so comfortable!!!
Same with paint:
Same μ-value but extra coats add more vapour resistance.
So don’t ask “Is it breathable?”
Ask: HOW breathable & HOW thick?

[ilias igoumenidis @igou]

Before thinking internal wall insulation, start with this question: “What’s the wall like underneath?” Old walls may be unstable, damp or covered with hard coats.

But, what should we do?

[ilias igoumenidis @igou]

You’ll never achieve #airtightness if your site looks like…a building site.

Dust kills adhesion while clean surfaces ensure strong bonds.

What to do?
Vacuum, wipe, prime - then tape.

(A clean site doesn’t guarantee success, but it sets the scene for it.)

[ilias igoumenidis @igou]

⚠️Water vapour turns to liquid when it touches cold surfaces, as the air cools and can no longer retain the same amount of moisture.

What to do:
👌Detail junctions to maintain warm surface temperature
👌Ventilate the space to lower room humidity

[ilias igoumenidis @igou]

When retrofitting cavity walls with external wall insulation, seal the cavity first.

If air moves freely in the wall, your insulation becomes redundant, like wearing a jacket with cold air blowing underneath.

[ilias igoumenidis @igou]

Internal cement plaster tends to restrict vapour movement, as it is far less diffusion-open than lime.

Use a capillary-active insulation, that can draw moisture from the wall, helping it to dry even through a cementitious layer by enabling evaporation to the inside.

[ilias igoumenidis @igou]

Window reveals, intermediate floor & partition wall junctions deserve extra attention.

They’re small areas that often decide whether a retrofit succeeds or fails.

[ilias igoumenidis @igou]

Doubling insulation from 100 → 200 mm gives less benefit than 50 → 100 mm,
which gives less than 25 → 50 mm.

Think diminishing returns and allocate your client’s budget wisely.

(If you’re aiming for Passive House: different story, different ball game.)

[ilias igoumenidis @igou]

Keep all layers continuous to prevent water ingress, thermal bridges, air leaks.

Weathertightness, insulation, airtightness

Continuity is what makes the fabric perform, not just the materials.

[ilias igoumenidis @igou]

Complex specifications look clever on paper, until someone tries to build them.

Simple build-ups mean:
👌 Fewer errors
👌 Better performance
👌 Happy contractors
👌 Happier clients
👌You sleep well!

[ilias igoumenidis @igou]

Materials that let water vapour move through by diffusion
(not air) are called:

✔️Vapour-open

✔️ Vapour-permeable

✔️ “Breathable”

✔️ Diffusion-open

✔️ Moisture-permeable

✔️ Permeable

✔️ Low vapour resistance

[ilias igoumenidis @igou]

Keep the Vapour Control Layer (VCL) on the warm side of the wall, roof or floor.

It holds water vapour within the warm interior, preventing it from cooling and condensing into liquid inside the building fabric, where it could cause moisture damage over time.