Flue or Chimney

Slig

Anybody know where I can get a defination of the above.
To me a flue is an outlet that doesnt pass through the roof while a chimney does.
Am I wrong?

topcatcbr

Its all about size (area to be more correct) Ill get you a def soon.

muffler

Interesting point but I dont think it has anything to do with roofs.

The flue would the actual channel that transfers the products of combustion to the external air while the chimney is a structure (for want of a better phrase) that houses or encases the flue.

topcatcbr

2 VENTILATION RATE [’Ventilation’ tab] The ventilation air change rate, expressed in terms of air changes per hour (ac/h), is the rate at which outside air enters or leaves a building. DEAP requires a reasonable estimate of the air change rate in order to calculate the ventilation heat loss rate (expressed in W/K) and its effect on the overall heating requirement. The actual ventilation rate depends on a large number of factors, many of which may not be known precisely (e.g. permeability of materials and inadvertent gaps and openings in the structure) and in most cases cannot be assessed from a site survey or from plans. These factors comprise both background air infiltration or leakage characteristics and ventilation features intentionally specified and provided in the dwelling. The air infiltration rate can be assessed either from a permeability test (also called an air leakage pressure test: Section 2.3) or, in the absence of a pressure test, using the “structural air tightness” section of the DEAP ventilation algorithm. Such a pressurisation test is carried out with all designed ventilation openings, flues, fans etc. sealed up and inoperative. This component of overall air change rate represents only background air leakage into and out of the dwelling. To calculate the component of overall air change rate due to individual ventilation features (“openings”, including fans) intentionally provided in the dwelling, the ventilation algorithm requires the information on the numbers of chimneys, extract fans, open flues, passive vents and flueless gas fires to be entered in the software. For the purposes of calculating overall ventilation rate, the individual contribution from each of these features is given in Table 2.1 below. Table 2.1 Ventilation rates Item Ventilation rate m3/hour Chimney 40 Open flue 20 Fan (intermittent) 10 Passive vent 10 Flueless gas fire1 40 The degree of sheltering of the dwelling is taken into account (Section 2.5). The overall ventilation air change rate is finally adjusted to take account of the type of ventilation provision in the dwelling, in six categories: Natural ventilation Positive input ventilation from loft Positive input ventilation from outside Whole-house extract ventilation Balanced whole-house mechanical ventilation, no heat recovery Balanced whole-house mechanical ventilation with heat recovery 2.1 Chimneys and flues Ventilation rates for chimneys and flues should be entered only when they are unrestricted and suitable for use. A restricted chimney would be permanently blocked. Temporary restrictions are ignored for the purposes of DEAP assessments. Examples of permanent restrictions would include brickwork, plasterwork or timber panelling fixed in place. The specified ventilation rate includes an allowance for the associated permanent vent for air supply, so this vent should not be entered separately. 1 Note that for flueless gas fires, for health and safety reasons, it is required that both a high level and low level permanent vent are installed to ensure the supply of oxygen for combustion and to dispose of the resultant fumes and water vapour.
For the purposes of the DEAP a chimney is defined as a vertical duct for combustion gases of diameter 200 mm or more (or a rectangular duct of equivalent size). Vertical ducts with diameter less than 200 mm should be counted as flues. The following are also counted as flues: a chimney for solid fuel appliances with controlled flow of the air supply; a chimney with open fireplace having an air supply ducted from outside to a point adjacent to the fireplace; a flexible flue liner sealed into a chimney; a chimney fitted with a damper; a chimney fitted with an open-flue gas fire where the flue products outlet is sealed to the chimney; a blocked up fireplace fitted with ventilators (if ventilator area does not exceed 30 000 mm²) Ventilation rates should be entered only for open flues; they should not be included for room-sealed (e.g. balanced flue) boilers or room heaters. A room heater is considered to be room sealed if it does not have any air exchange with the room in which it is situated.

Slig

muffler wrote: »

Interesting point but I dont think it has anything to do with roofs.

The flue would the actual channel that transfers the products of combustion to the external air while the chimney is a structure (for want of a better phrase) that houses or encases the flue.

That was my original assumption until I did my BER course and found that a flue gave you a better rating than a chimney and that it should be an option in the suggested improvements that all chimneys be changed to flues. (I didnt ask for clarification because they werent talking to me after the passive stack ventilation incident:D). Then I read in TGD part J that a flue shouldnt pass through the roof space and this got me thinking.

Is a chimney just a large diameter flue, or must a flue be smaller diameter and closed by an appliance?

No6

Slig without reading Topcats extract for the DEAP manual I think you may be slightly confusing the flue /chinmey thing. For the purposes of part J a flue is a pipe carrying the products away from a fire and can be just that a metal pipe. A chimney is a solid non combustable structure which contains a flue and so can pass through roofs.

For the purposes od DEAP a chimney refers to the actual diameter, over 200mm dia it is a chimney under 200mm Dia it is a flue and gives different results in terms of ventilateion rates. An open fire is rapidly becoming a thing of the past as they are brutally innefficient. How to piss off all Irish women in one easy step!!!:eek:

Slig

No6 wrote: »

Slig without reading Topcats extract for the DEAP manual I think you may be slightly confusing the flue /chinmey thing. For the purposes of part J a flue is a pipe carrying the products away from a fire and can be just that a metal pipe. A chimney is a solid non combustable structure which contains a flue and so can pass through roofs.

For the purposes od DEAP a chimney refers to the actual diameter, over 200mm dia it is a chimney under 200mm Dia it is a flue and gives different results in terms of ventilateion rates. An open fire is rapidly becoming a thing of the past as they are brutally innefficient. How to piss off all Irish women in one easy step!!!:eek:

I love that romantic notion they have of sitting in front of the open fire on a windy stromy night. They dont really take into account the mad dash for the truf/wood shed on same said night, holding flashlight between legs and trying to find the dry turf/wood in the minefield of buried catsh1t. then the mad dash back to the house with flashlight in one hand and bucket in another followed by attempt to open the door with either your foot or elbow all the time getting rained on. And then theres the ashes....

Anyway, So a flue (as categorised in DEAP) is basically a smaller diameter than the terracotta 250mm dia flue liner.

Mellor

topcatcbr wrote: »

For the purposes of the DEAP a chimney is defined as a vertical duct for combustion gases of diameter 200 mm or more (or a rectangular duct of equivalent size). Vertical ducts with diameter less than 200 mm should be counted as flues.

Bare in mind that this applies only for DEAP. Its merely a function of the software. "For the purposes of the DEAP" is the part that highlights this