Hygrometer - what do the numbers mean?

July 26, 2018


We're pleased to announce that we've added a new product to our EcoShop to help our community keep a warm and healthy home - the Hygrometer. This is a handy tool that allows you to record and read temperature and humidity levels in your home. But what do the numbers actually mean when it comes to keeping a healthy home? We asked our resident Home Performance Advisor Craig to help break it down for us...

Relative humidity is a measure of the amount of water vapour in the air.

Comfortable levels and a realistic target of relative humidity is between 40-60%. Relative humidity is considered to be high when it constantly exceeds 70% - which is actually very common in Wellington. This along with consistent temperatures of less than 16 degrees Celsius will result in mould growth.

World Health Organization recommends main lounge living areas to be heating between 18-21 degrees while occupied and bedrooms to be no lower than 16 degrees overnight (18-20 for young or elderly).

Relative humidity can be controlled in 3 ways:

  1. Reducing the moisture at the source. Use kitchen and bathroom extraction fans, ducted to the outside; dry clothes outside, ensure your clothes drier is ducted to the outside, do not use un-flued gas heaters, minimize indoor planting and fish tanks. Finally, keep ground moisture away from the house. Are there any drainage issues or broken gutters that may dampen the exposed soil under your house? In many cases, a moisture barrier is recommended under the house.
  2. Increasing the air temperature via heating and heat retention. Warmer air can support more moisture, reducing condensation on windows.
  3. Ventilating via mechanical systems such as Smart Vent or simply by opening windows at opposite ends of the house for 1/2 hr a day. Allow a good breeze through. Outside air, although cooler, is usually drier. You’ll find that cold, dry air take less energy to heat than warm, damp, moisture laden air.

A bit more science about relative humidity... Relative humidity is expressed as a percentage figure. For example, relative humidity at 60% means the air contains 60 percent of all the total water vapour the air can possibly hold at that temperature. If the amount of water vapour in the air stays unchanged, but you increase the air temperature of the room with additional heating, you will notice the relative humidity drop.

There you go! If you want to buy one (or more!) of these for your home, you can either pop into our EcoShop on Forresters Lane or buy one online - enjoy your healthy home!

Also in Ask an expert

Plastic Free July: let them eat cake!
Plastic Free July: let them eat cake!

July 25, 2018

Here's a home tip about starting a positive culture…making, eating and sharing CAKE. While also reducing your plastic use. It helps to be positive, rather than just focusing on the problem. Read more from our expert Vishal.

Continue Reading

Plastic free July: making your pantry plastic-free
Plastic free July: making your pantry plastic-free

July 17, 2018

Using glass jars to store food in your kitchen, instead of plastic, is a great Plastic-Free July idea. Read more from our expert Marion.

Continue Reading

Is your home properly insulated? 9 top tips to stay warm this winter
Is your home properly insulated? 9 top tips to stay warm this winter

June 20, 2018

Wondering why your house is cold and what you can do about it? The answer could be poor insulation, even if you think it's up to scratch. Here are some top tips to overcome common home insulation problems, based on our 15 years expertise creating warm, healthy homes.

Continue Reading

Sign up for our newsletter

Get Sustainability Trust's news, events and specials straight to your inbox every month