Helpful Information


Negative Air Pressure ............................ and the energy efficient airtight houseNegative Air Pressure----What is it?

Negative air pressure is a phenomenon discovered after the energy crises in the seventy’s, and caused when houses began to be built to more energy efficient standards.

This type of house will show some or all of the following symptoms;

  • Back drafting of combustion appliances such as the fireplace, wood stove, gas hot water heater and even the furnace

  • Mold, mildew and moisture as well as condensation which shows itself around windows or on walls

  • A lack of fresh air, a musty smell, lingering odors around the house

  • Stagnant, stale, heavy, air causing high humidity and condensation

  • A rush of air or draft when opening an exterior door (pic) 3air.jpg +(1) enlarge

These are all typical symptoms of an energy efficient airtight house, or sick building syndrome, but they are just that symptoms and very few people realize the health problems arising from living in an airtight house.

In a house that lacks a source of fresh air a phenomenon called negative pressure is created. This is caused by to much air is leaving the house through various sources and the inability of replacement air to have an easy access into the house replacing air and oxygen used when the living conditions such as heat rising and exhaust fans operating, combustion appliances and people are using air and oxygen. These symptoms of an energy (pic) stack.jpg+(1)enlarged efficient sick house can be eliminated. If you cure the illness with fresh air, like opening a window, the symptoms will disappear by themselves.

































For reliable operation, all combustion appliances installed in well-sealed houses 
should be provided with an adequate source of air. 

Fireplaces present a particular problem because they consume so much room air, especially when the doors are open. Even with doors closed, most fireplaces need large amounts of room air. 

Fireplaces also tend to be more prone to back drafting. For this reason, it is always a good practice to provide a fireplace with close-fitting glass doors and ensure a good source of air for combustion.

Negative Air Pressure.................... and the silent killer

              "Houses need to Breathe"



The neutral pressure plane is often, but not always, located at the vertical mid-point of the house. A house with similar leakage rates at all levels will have a neutral pressure plane at approximately its mid-point.

A house with a well-sealed ground floor but a leakier upstairs will tend to have a neutral pressure plane higher than the mid-point, and a house with a leaky ground floor and sealed upstairs will have a lower neutral pressure plane.

The neutral pressure plane tends to move towards the leakiest level of the house. This movement of the neutral pressure plane explains why opening a ground floor window can improve chimney flow and prevent back drafting in a ground floor woodstove or fireplace. The open ground floor window represents a large enough leak to bring the neutral pressure plane down to basement level, reducing or temporarily eliminating the negative pressure the chimney has to work against.

If you experience down drafting open a door or window for a few minutes and watch how easily this works to change the neutral pressure plane and prevents that unpleasant smoke filled room if you do it before you light the fire.

The first two suggestions are simple ways to test if you have negative air pressure before lighting your fire and the third is a solution for temporarily eliminating the problem.

1) hold your hand inside the fire box and up near the damper (make sure the damper is open) and see if you feel cold air coming down the chimney

2) Light a good size sheet of paper and hold it in that same position up near the damper; if the fire goes out or the flames are being blown back the stack effect is happening.

3) Open a window or door to balance the air pressure in the room; light another piece of paper and hold it in the fire box the flames should draw up the chimney if the pressure has been equalised (leave the window or door open until you determine that a good draw has been established in the chimney) 

So now you understand the stack effect in your house and you are be able to temporarily eliminate the 
problem of lighting a fireplace or wood stove in the ground floor.

(although in an inefficient way) But remember the warm air in a house tends to rise, producing a stack effect similar to the draft in chimneys. The resulting negative pressure in a basement can cause venting problems in all combustion appliances located there; so what about your furnace that cycles on and off continually, the above tests and remedies will not be a practical solution.



All you need to know about installing and operating your wood burning or multi fuel stove.

When making an investment in stoves, it is important to have all the facts 'at your fingertips.'  Ireland Stoves we want you to be completely satisfied with your purchase, so the following information is provided to help you make the right choice.

Before installing your new Ireland Stoves stove
For safe operation, consider the following

Protection of combustible materials
It is important that you never leave any potentially combustible materials or fuels near the stove..

You should be aware that not all combustible materials are immediately visible. There may, for instance, be wooden studs in the partition walls adjacent to the stove. Indeed even so-called fire-resistant materials may eventually burn and so should be treated in the same manner as combustible items.
The stove itself should be situated on a non-combustible surface with a minimum thickness of 10mm (approx 3/8”) and should extend to 460mm (approx 18 1/2”) in front of the stove and 200mm (8”) at the back and sides of the stove. This floor protection must also be placed directly under any horizontal length of flue protruding from the back of the stove with a further minimum 50mm (2”) around this area.

The following clearances should be maintained from all combustible materials:
Back of stove - 760mm (approx 31”)
Sides of stove - 510mm (approx 21”)

Adequate provision of air
It is essential that you ensure an adequate and proper supply of air to the stove for the stove to be safe and to operate efficiently.  In some cases this may involve  providing an additional outside air supply to the room, especially if there are extraction units such as cooker hoods or clothes dryers in the vicinity. Otherwise, a less than adequate  air supply could mean that the fuel is burned inefficiently causing smoke and blackening of the glass, with the possibility of smoke entering the room. Simple check:  open a door or window in the room to see if the stove then burns more efficiently.

A well sealed flue system
The chimney and flue are the means by which the combusted fuel is taken away from the stove, as well as providing the draught that is needed for the stove to work efficiently.

You should not use aluminium or galvanized steel pipes for your stove flue and you should only  burn approved fuels. Make sure you  use the manufacturer’s recommended flue diameter - in the case of the Horse Flame and Olymberyl stoves, this is sometimes 125mm (5”) but more usually 150mm (6”). It should never be less that 125mm (5”).
If  a stove is to be used with a traditional chimney system, always use an approved non-combustible ‘register plate’ - normally of 1.5mm thick steel -which will seal the space at a point below where the stove flue pipe end protrudes into the chimney void. These are available with pre-cut 125mm and 150mm diameter holes. All joints in the flue system should be sealed with ‘fire cement’ and / or an appropriate fire resistant ‘rope gasket’.

Make sure that pipe bends in the flue system are kept to a minimum and we recommend that no more than two on any installation as this could restrict  the smooth flow of air and combusted materials.

Flues should never pass through ceilings, floors, attics, roofs or combustible walls without adequate and approved insulation being provided to protect potentially combustible materials. In these instances always refer to your local building and fire regulations.

The open end of the flue system must be always be above the height of the apex of the building and any other potential obstructions which are within 3m (10’) of the flue, such as overhanging trees. When using a traditional chimney make sure that this has been thoroughly swept and that it has not been ‘capped’ or its original operating height reduced.

Plumbing a stove with a boiler
To be sure of the safe and efficient operation of your stove we strongly recommend that you have it installed and connected to the heating system by a plumber or heating engineer with recognised approvals. All plumbing should comply with relevant national standards. All our stoves come with comprehensive and easy to follow fitting instructions and installation should therefore not present any problems to a suitably qualified person.(You may request a copy of these instructions to be emailed to you if you contact Ireland Stoves)

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