16 Nov High star rated homes – what this means for you and you wood heater?
High star rated homes – what this means for you and you wood heater?
Since 2013 new homes must achieve an average 6-star rating
The Nationwide House Energy Rating (NatHER) is a Star Rating from 0 to 10 that measures how energy efficient a house is, based on its design and heat loss.
The rating applies to the building envelope: the roof, walls, floor and windows.
A focus to achieve a high star rating home is reducing heating and cooling costs.
Major factors to get these results is heat loss,
- through draught proofing doors and windows
- and high R rated insulation for walls, ceilings and roofing
What draught proofing and high R rated insulation does, is make your home air-tight to prevent heat loss
Wood Heaters need air…
Your wood heater need 2 types of air.
Air for combustion
-
- An average large wood heater will require up to 6,000ltrs of air per day for combustion
- Based on 4 high burn cycles / 4 medium burn cycles and 4 low burn cycles
- An average large wood heater will require up to 6,000ltrs of air per day for combustion
Air for cooling the flue
- A “default” triple skin, air cooled flue kit can peak using 420ltrs of air per minute when the heater is on a high burn cycle
Default air cooled triple skin flue kit
What you need to do to put a wood heater in a high efficient home…
In a NatHER 6star rated home, installing a wood heater, you need to address the air required for both combustion and the flue system
Combustion air
As all wood heaters require air (oxygen) for the fire (combustion) a traditional wood heater brings this air in via an air control over the door
# note: the main reason this air control is over the door is to achieve air wash to keep the glass clean during burning
- This air is provided by the air from your room
Another way you can get the air (oxygen) required for your wood heater is via a vent, or duct, connected from outside and venting straight into the air intake of your wood heater
- This system is called Outside Air
Outside air (or combustion air) then feeds directly into your wood heater, so no air (oxygen) is used from your home for combustion
This system is also perfect for homes that have issues with Negative Pressure
Wood heaters with the outside air option not only fix issues with NatHER star rating, and negative pressure issues, but with over 6,000lts of air (oxgyen) used per day – wood heaters with outside air also will prevent draughts in a home caused by traditional wood heaters
Outside air for wood heaters are available on a number of brands, traditionally these wood heaters are made in the UK, Europe, Canada and Nth America where homes are built for extreme cold environments.
Outside air for wood stoves wood heaters
Air for your flue system
All wood heaters require a flue system, and in Australia traditionally this flue system is called a DEFAULT, triple skin air cooled flue
To cool the wood heater flue down as it penetrates the ceiling/roof, air is used to cool to pass through the different flue skins.
As an average working temperature of any wood heater flue can be between 180°C and 300°C (with a maximum peak temperature of 750°C) this flue is required to be cooled down to a maximum outside temperature of 83°C as it passes through the ceiling cavity
The Australian standard AS/NZS 2918 requires an air cooled flue to have a min of opening of 2,500mm to allow the flue to negative pressure enough air to cool the flue down.
- This works out to be a max of 420ltrs of air per minute when the wood heater flue temperature is over 300°C
For any new home (or home renovation), having an air tight flue penetration where the flue goes through the ceiling is critical
- For a NatHER 6 star rated home : Insulated ROOM SEAL FLUE kits are the best option to not loose the star rating to your home. These are standard in the UK, Europe, Canada and Nth America where any heat loss to the home is critical in extreme cold environments
Insulated ROOM SEAL FLUE kit for wood heaters
- Are 100% air tight for the home
- These are tested to AS/NZS 2918
- Offer a complete air tight solution
- And will increase the heaters performance by 8%
- (the loss of 420ltrs of air in a traditional default triple skin flue kit calculated to a 8% heat loos off a traditional wood heater)
Negative Pressure issues for new NatHER 6 star rated homes
As a sealed vessel (this is basically what a NatHER 6 star rated home achieves) any mechanical devise that sucks can cause a NatHER 6 star rated home to become negative pressured
These devises include
- Exhaust fan in the kitchen
- Exhaust fan in the bathrooms
- 2 story homes
As the home becomes negative pressured, the home is in need to recover to balance the pressure and this is where wood heaters become an issue
As the home tries to equalize the homes pressure it will suck air from anywhere it can, and as your wood heater is vented to the outside, it’s not uncommon for wood heaters to then smoke the house out
- This is known as negative pressure – down draught
To address this issue, sealing the wood heater to your home is critical
- Seal the air intake with an outside air for combustion
- Seal the air loss to the room with an insulated flue kit
outside air for wood stoves wood heaters
For wood heaters that over both
- Outside air for combustion
- Insulated ROOM SEAL FLUE KIT
CHECK OUT THIS LINK https://pivotstove.co.nz/collections/wood-heater/high-efficient/
For more information on air sealing your home, Unity Home Group (Alaska) Air Sealing Your Home: A Complete Guide to Identifying and Sealing Air Leaks
INFORMATION for this article was soured through
For more information on heating running costs https://www.sustainability.vic.gov.au/You-and-your-home/Save-energy/Heating/Heating-running-costs
About the author
This article was written by Greg Parker-Hill .
Greg is a licensed plumber with over 35 years experience / and 6th generation within the HVAC industry
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