FAQs
Disclaimer: While we believe the advice on these pages to be appropriate, anyone considering purchasing products or services is advised to do their own research into the options available to them.
Clicking on a question will show the answer down the page:
I have foil installed under the floor of my house. Is this an effective type of insulation?
Does gas heating create a lot of moisture? We have gas for heating and cooking.
Are heat pumps better than gas heaters?
Q: My rental unit has concrete block walls and a high ceiling (no insulation) and there are big windows and ranch sliders. Although I love it in summer, it is freezing in winter. I don’t want to move again, but need to be warmer. What can I do? I don’t want to spend a lot of money.
A: Buy or make some detachable thermal backed linings for the existing curtains (you can take the linings with you when you move on). These clip onto the existing curtain hooks and use the same tracks, a fabric or curtaining shop can help you with this. Close the curtains at sunset to keep the heat in.
Extra rugs on the floors and a textured wall hanging/small rug hung on the concrete wall behind where you sit will increase the thermal comfort in your home. If your living area is very large, screen off a smaller cosier area to heat. Use a heater on a timer to warm the bedroom half an hour before going to bed. An electric blanket is also a low cost solution.
Talk to your landlord about installing an efficient clean heat system (heatpump/pellet fire/flued gas) and ceiling and/or underfloor insulation. There are grants available to landlords for insulation and heating - call the Advice Centre for more information.
If this fails, your best source of heating may be a radiant electric heater. A radiant heater will warm whoever is directly in front of it. They are ideal if you only want to heat yourself and are sitting in one place, such as watching TV or working at a desk. We do not recommend portable or unflued gas heaters due to high levels of moisture produced during operation, and noxious combustion gases.
Q: I have foil installed under the floor of my house. Is this an effective type of insulation?
Foils are a cheap and reasonably effective method of under floor insulation. They have been the industry standard for new buildings and retrofits for many years. Foils work in three ways:
- Radiated heat from the floorboards is reflected back
- The foil captures a cushion of still air which acts as an insulator
- Draughts blowing up through the floor boards are eliminated
Foil products are usually stapled and strapped to the floor joists, and must be installed correctly to minimise any potential for air movement between the foil and the floor boards. Foils provide some protection from rising damp and provide adequate insulation from draughts and external air temperatures, provided the foil is intact and joins are taped securely to stop draughts.
Foils generally have a life of 15 years, but their performance can be seriously diminished if they are damaged. Some foils are easily ripped (cats and plumbers are two of the main culprits) and the insulating properties tend to reduce over time as the upward-facing surface loses its shine. However there are several foils under tradenames “Astrofoil” “Aircell” and “Silversark” that incorporate plastic membranes in their construction and are much tougher.
If the foil under your house is ripped or corroded, you might consider replacing it with a bulk insulation (such as fiberglass, polyester, or polystyrene). While these are more expensive, they are much more durable and are rated for at least 50 years. If you do decide to reinstall foil, then you must be extremely careful when stapling the foil. There have been several deaths from electrocution by DIY installers stapling through live cables. It will always be safer to disconnect power when you install under the house, but you will still need to check that the foil has not livened up (use a “volt stick” or multimeter) when the power is switched back on.
Q: Does gas heating create a lot of moisture? We have gas for heating and cooking.
A: All un-flued gas heating and cooking releases moisture into the air, about 1.6 kg of water for every kg of gas burned. Flued gas heating vents all combustion products outside and will not result in an increase in internal moisture. With a gas cooker, this isn’t usually an issue, as the hobs or oven are in use for a relatively short time, and many cooktops and ovens have extractor vents and hoods.Un-flued gas heating releases a lot of moisture in the home which both makes the house harder to heat and also can lead to condensation and mould, crying windows are a common complaint. It is very important to provide ventilation in rooms where un-flued gas heating is used, due to the combustion process slowly using up oxygen and releasing pollutants. Long term these heaters are best replaced with flued gas heaters or other heating options. Gas heaters are not any cheaper to operate than plug-in electric heaters and because of the extra moisture produced are actually less efficient.
All portable gas heaters are un-flued, as are some of the smaller wall mounted models. If you are not sure whether your gas heater is flued or un-flued, contact the Advice Centre.
Q: There is a lot of condensation in my house - the window sills are covered in water every morning. My son has asthma and I’m sure the damp isn’t helping. I’ve heard installing a mechanical ventilation system can help but I can’t afford it. Do you have any low cost suggestions?
A: It is very important to understand how and why condensation forms in a house – here’s a brief explanation.
Condensation forms when warm moist air meets a cold surface (eg window panes). This effect is just like the dew forming on the grass on a cold night. Inside the house windows are the coldest surface (about the same temperature as the outside air) and when they cool down below the “dew point” of the air inside the house, condensation forms – “crying windows”. There are two main ways to avoid or reduce this condensation – reduce the amount of moisture in the house and/or raise the temperature of the air and internal surfaces.
Practically this can be achieved by a combination of the following:
- Producing less moisture in the house from household activities
- Reducing the amount of moisture getting inside from outside
- Ventilation
- Insulation
- Heating
- Double glazing
Mechanical ventilation systems introduce “outside” air into the house. This outside air is almost always drier than internal air and tends to force wet internal air out through gaps in the building. However, ventilation systems cost serious money, perhaps $2000 - $3000. HEAC strongly recommends addressing the causes before spending money on an appliance you may not end up needing. Ask for a fact sheet on moisture issues from the HEAC advisor.
Produce Less Moisture Inside the House
We all produce moisture during our everyday activities in the home (breathing, washing etc) and it would be impossible to prevent all moisture, but you can reduce the amount you produce by:
- Limit the time spent in the shower
- Limit the number of pot plants in your house
- Dry your clothes outside
- If you use a clothes dryer, make sure that it is vented outside
- If you must dry your clothes inside, do this in a well ventilated room with doors closed to the rest of the house
- Close the doors to the bathroom and kitchen when you are bathing or cooking
- Always wipe excess moisture from windows - moisture collecting on the frame which may cause rotting. It may also re-evaporate during the day, raising humidity levels and making condensation worse when the room cools down.
- Use extractor fans in “wet” areas such as bathrooms, kitchens, and laundries
Moisture from Outside
Moisture can enter the house through gaps in the ceiling envelope – leaky homes are an example of moisture entering the building. Check that all gaps and pipe penetrations are sealed against the weather, that rain guttering is not leaking and that it directs water away from the house. If your under floor or basement is damp, and there is inadequate ventilation, laying a polythene vapour barrier will reduce the amount of moisture entering the house through the subfloor.
Ventilation
Ventilation is really important. Air moving in from the outside is drier than air on the inside. - even on a rainy day, opening two or more windows a small amount to encourage a cross draught will reduce the buildup of internal moisture. Fixing security stays to the windows may allow you to leave windows open while you are out.
Heating, Insulation, and Double Glazing
And lastly, heating and insulation are key. If your house is warmer then there is less likelihood of moisture condensation. Warm air can hold a lot more moisture than cold air, but remember that if you don’t reduce moisture or ventilate your home, the moisture in the air will condense on cooler surfaces.
Double glazing is also an option. This reduces condensation in two ways –
The internal glass is warmer (and therefore less likely to attract condensation) than a comparable single glazed window . This is because it is insulated from the outside air
Double glazing reduces the overall heat loss in a home thus reducing the likelihood of condensation.
Other Options
And if everything fails, try a dehumidifier (but be sure windows are closed when you use it) and last of all request an inspection by a company who deal with mechanical ventilation systems. But call the Home Energy Advisor first, we could save you a lot of money and worry by troubleshooting the basics first.
Q: My 1980s house has a chapel ceiling (the inside profile follows the line of the roof), which I don’t think is insulated. It is extremely cold in winter. Is it possible to add insulation to a roof like this?
A: A lot of your home’s heat (up to 45%) can be lost through an un-insulated ceiling. If your chapel ceiling was not insulated at the time it was built, you have a few choices:
1. It may be possible (if there is enough space between the rafters and the ceiling lining) to inject insulation into the cavity. There are companies in the Yellow Pages specialising in this service.
2. Employ a builder to take the roofing iron off and fit bulk insulation between the ceiling joists batts, then replace the roofing iron. This will not be cheap but you will definitely save on your power bills (typically up to $400 per year savings) and your home will feel warmer and more comfortable.
You could drop the ceiling and install insulation from the inside. This is certainly easier if you have exposed beams, as you can install bulk insulation between the beams and sheet over the beams.
Q: I’ve been told that the ground under my house is damp and that I should get a polythene moisture barrier installed so that the house is drier and easier to heat. Can I do this myself?
A: First check your underfloor ventilation. If you have an open underfloor or “hit and miss” battens, there is probably plenty of airflow and little value in installing a moisture barrier. If your have a concrete ring foundation or little ventilation, find out why your underfloor is damp and if possible deal with any plumbing or drainage problems first (get these checked by a professional).
If there is nothing you can do (without calling in the cavalry) because you are in a low lying valley or the house is cut into a hillside, a polythene moisture barrier can help keep your house dry and warm inside. In some cases it can make a substantial difference to the moisture levels inside the house.
Polythene sheeting is available from hardware stores. Purchase the thickest grade (250 micron is best) and cut it into approximately 2 metre strips to lay between the piles, cutting slits along one side to fit around piles. Slits need to be taped up with polythene tape around the piles, and the overlaps between neighbouring strips also need to be taped. Weedmat pegs (available at hardware stores or garden shops) can be used to peg down the polythene at regular intervals (every 2 metres or so), rocks or heavy objects will also do.
Q: Are heat pumps better than gas heaters? We have a large flued gas heater in the living area and another smaller one in the dining room. We are thinking of replacing these with heat pumps.
A: To answer your question, consider your motivation. Is it cost? Is it control? Is it functions? Is it aesthetics? Efficiency and cost are usually the reasons people give for switching to heat pumps. While this is a valid reason to switch from portable electric heaters to heatpumps, it is a different story for other heaters such as gas.
On a cost basis, heatpumps and gas heaters are pretty similar. Heatpumps have an average efficiency of around 250% (though this decreases with air temperature - lower efficiencies in colder climates). Assuming an electricity cost of 22c/kWh, the cost per unit of heat is around 9c/kWh. Gas fires generally have an efficiency of around 90% and a cost/unit around 8c/kWh, and thus a cost per unit of heat of around 9c/kWh.
Other points to consider include disconnecting from the gas mains entirely, which you can do if you only use gas for heating, to drop your supply charge. However, if you use gas for other appliances you will continue to pay your gas supply charge and start paying a higher electricity connection charge as you will move to high-user electricity supply charge. The Advice Centre can run a quick calculation for you based on your individual situation. BUT remember if you are installing a heatpump or two, the cost to install the units should be taken into account. It may take a very long time to recoup the costs of installation.
Heatpumps come with options that may be attractive, such as timers, thermostats and allergen filters; in summer they can also dehumidify and cool, though this is rarely needed in NZ and will add to your power bill. They also use fans to distribute heat (so there will be a breeze and some noise) and some people find the look unattractive. A flued gas heater is generally capable of putting out more heat on really cold days than a heat pump.
If you do decide to go with a heat pump, make sure the model you are purchasing is sized appropriately for the volume of the room you wish to heat. We would recommend having a look at some of the Consumer reviews on different models and choosing a company that has been in business for a while.
If you would like to discuss your heating options in more detail, contact the Advice Centre. If your home was built before 2000, you may be eligible for financial assistance or government subsidies (depending on household income levels- if under $100,000 for 1-2 earners, under $140,000 for 3+ earners).
