Temperature and Tenants

Managing moisture in rental properties.

My vision is for everyone in Aoteraroa to live in warm dry comfortable healthy homes.

Not houses, homes!

I have a rental property in Richmond, Christchurch where I’ve been almost tearing my hair out trying to manage the temperature, humidity and carbon dioxide levels with the occupants.

The previous occupants didn't have an issue with moisture or mould, despite spending three winters in the house. The current occupants encountered mould within six months of moving in. They didn’t say anything however, I noticed it during an inspection.

So we added some monitoring devices to help educate us both on what was going on and what constitutes healthy living.

Despite my best efforts, after three years this was proving to be frustrating and frankly, fruitless.

Comments like “now I have a dehumidifier, I don’t need to use the heat pump,” attest to the reasons why.

Earlier this year, in late summer during an inspection, I noticed substantial mould on the ceiling in the south east bedroom.

You don’t expect mould in summer!

This made me get up in the roof space to see if the roof was leaking.

Good news. It wasn’t.

Bad news. There was no insulation whatsoever over this area of the ceiling in that bedroom.

I was horrified!

Now this is the room furthest away from the heat pump. The coldest room in the house. The smallest tamariki bedroom.

Nearly as bad, was that the original pink insulation had slumped and was generally gappy across the board.

Something had to be done!

In May, working together with the occupants, we installed 180mm of R4 Terra Lana Products Ltd. insulation in the roof space, taking care to make sure we got as tight and complete as coverage as we possible could, while tidying up the existing stuff underneath.

(You can see the dotted vertical line in the graphs above indicating when the insulation went in.)

However, I could see I was solving one problem by creating another, in the constant Kiwi way.

All that additional insulation, while it might make the house warmer in winter and cooler in summer, would likely cause condensation issues in the roof cavity, unless the high humidity was handled better.

The final trigger was finding that rats had eaten through the existing extraction ducts!

So, last Friday 14th June 2024, our first mechanical ventilation with heat recovery system was installed. Not in our own home (that's very high on the wish list), but in this house. (If you want to learn a bit more about heat recovery follow this link) https://www.healthyhome.kiwi/the-clever-heat-exchanger

The beauty of this system is that it has a tenant module, so it can't be tampered with. There is no off switch, short of pulling out the fuse.

Now, Passive House purists, I know its not a certified system, I know its installed in the roof space and I know that this is horrible ducting, BUT... I can now monitor this entry level system and see how well it works.

Will it work better than what was there before?

Is it recovering heat?

Is it drying out the house and reducing CO2 levels?

Follow me and lets see!

One key point, when installing mechanical ventilation systems, you must under cut the doors.

Why?

If you refer to the design above, the orange ducting is sucking out moist air from the kitchen, laundry, toilet & bathroom.

The green ducting is blowing fresh filtered tempered air into the dining room, lounge and the three bedrooms.

One is pushing and one is pulling and for the push to equal the pull the airflow must be able to transfer from one to the other under the doors and across the hallway.

Surprisingly, this is not a service the ventilation company offers, because it's a necessity to ensure the system works as designed.

I started with 20mm, but found that there was no timber left in the bottom of these hollow core doors, so settled on 15mm.

However, what I don't have is control over the heat pump.

This is not a heating system. It's a ventilation system. They are different and should always be separate.

The tenants still need to raise the temperature to have a warm, healthy home.

I've done all I can, it's now down to the way they choose to live in their whare.