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Alan in Marlborough, New Zealand

In winter when the heat pump (air con) inside unit heats the inside of the house the outside unit blows cold air across the outside wall and window of a bedroom. There is black mould spotting on the weatherboard outside wall and on the curtains inside the window. Today I will adjust the outside unit at an angle so the cold exhaust blows away from the window. I discovered the mould when I was painting the window frame. I am certain that the influence of cold air in winter when heat is needed in the house gets black mould going with health problems for residents. I will try a 3% spray of hydrogen peroxide on the curtain liner on a small trial patch to see how that works. HHOO is a bleach.

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4 thoughts to “Alan in Marlborough, New Zealand”

  1. Alan, thank you for stopping by and sharing your story! How did your trial patch go? Did you notice any improvements to preventing condensation with your adjustment of the unit exhaust?

  2. Early days yet. Resene supply “Moss and Mould killer” concentrate. 1 litre $10. Dilute with water 1:5. I brushed it on the outside weatherboards and within two minutes the spots were gone. Immediately wash off with hose. Can be used inside and out. Thanks for comment on hydrogen peroxide. It did not remove the spots. I will try the powerful Resene diluted fluid on a trial patch on a curtain. These are costly curtains! I was surprised by the extent of mould spots on just about every face of the house. It looks like grime until close inspection. So far I have treated most of the house outside and I still have half a litre of concentrate. My wife and I, 80 (ish) both have had itchy eyes, running nose, occasional coughs, to a limited extent for weeks now. We blamed weather and age.

  3. Same day, later. The curtains are good quality with a white lining lightly tacked on. Mould spots clearly visible. I tried using the Moss and Mould killer, diluted 1:5 on the curtain liner. If the lining rots, sad, but if I hadn’t tried and the spots remained it would still need a new liner. I decided it is worth a try.

    The pattern of spots line up with the window cill. Sash windows. My wife opens the window about 2 inches to ventilate the room. There is a distinct ‘cut-off’ line at cill height where the spots go upwards on the liner in vertical tapering patches. These I deduce are the folds of the liner resting on the window where there is condensation. The folds away from the damp double glazing are clear of spots. The liner intercepts the airborne mould. The rest of the room is clean.

    Two curtains. I used a ply board as a scrubbing board to separate liner and curtain. I cleaned one curtain liner by sponging on the dilute cleaner. It requires repeated rubbing to eradicate the spots which it does very well. I sponged it off immediately afterwards with clean water. The damp curtain in situ is now resting over a hard back wooden chair to separate curtain and liner. Underneath is a small fan heater blowing warm air upwards between the curtain and the liner.

    An earlier question, did directing the cold airblast from outdoor unit stop the condensation? At that time 3-4 days ago the air was very cold and humid. Now it is not so cold and not so humid. I was preparing the window cills for painting when I noticed the mould spots. for several days I could not continue as the cills were quite wet until mid afternoon on a sunny day. That wall faces South in NZ which is similar to North in northern hemisphere. No sun in winter. Today the cill was dry at 08.00. The aircon unit was facing east, now it faces ESE. The airblast rustles bushes 12 feet away from the unit and 12 feet away from the wall and window.

    Sorry about the length but surroundings affect outcomes.

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