How to fix shed condensation?

ksize

Hi There,

We have so much condensation drip onto our appliances and belongings in the shed and need to make it safe.

We've installed a whirly already but looks at what else we can do.

I've read about the films and taping it together but am concerned this will just send the drips to the wall where the PowerPoints are.

At some stage we will be enclosing part of the shed so want to ensure it's sorted so it doesn't create moisture problems where the insulation will be in the enclosed section too.

EricL

Hello @ksize

Thank you for sharing your question about condensation in your shed.

A whirlybird can certainly improve ventilation, but on its own it doesn't usually prevent condensation. Condensation occurs when the underside of the steel roof becomes colder than the dew point of the air inside the shed. As warm, moisture-laden air rises and comes into contact with the cold steel roofing, the moisture condenses into water droplets on the underside of the roof.

In your case, having exposed steel roof sheeting over a concrete slab with no insulation makes condensation much more likely. Even an older concrete slab naturally releases a small amount of moisture, while humidity also enters through open doors and gaps. Overnight, the steel roof cools very quickly, often becoming colder than the air inside the shed. When the warmer, humid air touches the cold roof, condensation forms and can eventually drip back down into the shed.

A whirlybird works best when there is also a source of fresh air entering the shed at a lower level. Without adequate intake ventilation through wall vents, eaves or other openings, the whirlybird has very little air to draw through the building, limiting its effectiveness. Even with good ventilation, exposed steel roofing can still develop condensation because of the large temperature difference between the roof and the air inside.

The most effective long-term solution is to create a thermal break between the steel roof and the air inside the shed. Installing a foil-faced roofing blanket, such as https://www.bunnings.com.au/earthwool-55mm-x-1200mm-x-15000mm-18m-space-blanket-r1-3-metal-roof-insulation-pack-of-1_p0810887 , beneath the roof sheeting is generally the best option, although this is easiest if the roof sheets are removed and reinstalled. If removing the roof isn't practical, installing foil-faced insulation such as https://www.bunnings.com.au/ametalin-1350mm-x-22-25m-thermalbreak-roof-and-wall-home-insulation_p0811234 or rigid insulation panels such as https://www.bunnings.com.au/foilboard-green-10-2400-x-1200-x-10mm-2-88m2-insulation-panel_p0125954 beneath the roof framing can also significantly reduce condensation. Adding additional low-level ventilation such as https://www.bunnings.com.au/builders-edge-600-x-450mm-aluminium-door-relief-grille-vent_p0064754 or https://www.bunnings.com.au/haron-300-x-300mm-silver-aluminium-pressed-wall-vent_p0814362 to complement the whirlybird will further improve airflow, but insulation is usually the single biggest improvement for a shed with exposed steel roofing.

I also suggest having a look at these discussions - How to fix condensation inside Absco garden shed? by @peter1959 and How to insulate a Colorbond garage shed roof and walls? by @Danson.

Just a friendly reminder to our New Zealand members that the use of Foilboard is prohibited.

Please remember to wear personal protection such as appropriate clothing, gloves, goggles and mask when handling insulation

Eric