Mushrooms on my roof!

[Polishicebreaker]

Good afternoon all, the time has come to prep and paint my roof. I have 2 old leaky mushroom vents. initially I planned to restore them, re-seal etc if possible or if not buy some nice chrome ones. I then had a chat with a fellow boater who advised me A: they are not essential to ventilation if one has sufficient ventilation from other means and B: they can be a pain in the arse to work around and make sure they do their job properly. With this in mind I'm considering doing away with them and replating the roof in their absence.

Any thoughts?? What does the BSS say about ventilation? "read the regs" I hear you shout ! ok ok....

 

Ed

[MtB]

Indeed. Why should I read them for you if you can't be bothered?

 

But in general they are there in order to achieve the correct ventilation so blanking them off would probably be counter-productive. I'm puzzled why yours leak though. Are they the very old type with no (or minimal) upstands to stop the rain splashing in?

 

 

MtB

[Polishicebreaker]

yes fair enough, I'll get my reading glasses out! Only one is actually leaking but it looks broken anyway. I was more concerned with dripping condensation in future and the extra work of paneling around them extra when they may not be the best way to ventilate.

 

They are the type with no upstands and screw directly to cabin roof.

 

cheers Ed

[MtB]

Ah so they don't actually leak, and you are worried about a future problem (probably non-problem) with condensation!

 

May I suggest if this is your biggest problem you are living a charmed life

 

 

MtB

[Dominic M]

You need to know the demands of your internal appliances (stove and cooker being the most obvious) and add that lot up. Divide by two and the figure you arrive at is the minimum requirement for FIXED high level and low level ventilation (each). Quite how you can achieve that without some form of roof vents I'm not sure. I think you might want to ask the person who told you that you could do away with your roof vents for the explanation in hard facts and figures.

[Polishicebreaker]

that sounds sensible thanks. I'll have a small gas boiler and a 5Kw stove in an open plan cabin thats around 30' x 10'. My friend suggested vents in the cabin sides rather than roof, also some in the doors. I also have wooden windows that are sealed but must provide some ventilation, hopefully not too much though if my Joinery is up to scratch!

[RLWP]

It's not hard to remove mushrooms when you paint. You can then restore them to shininess somewhere more convenient before screwing them back in place on a bed of sealant

 

Richard

Edited August 17, 2013 by RLWP

[Speedwheel]

It's not hard to remove mushrooms when you paint. You can then paint them somewhere more convenient before screwing them back in place on a bed of sealant

 

Richard

[Polishicebreaker]

thanks but thats not really a problem, It's more an issue of are they really necessary? I've just read BSS and they do specify an amount of high level ventilation so I'll research all available options. In the meantime back to the roof sanding.

 

many thanks

 

Ed

[RLWP]

OK, another aspect. Should you choose to have the holes welded up, you'll probably distort the roof. Making that look good is a nightmare, far worse than tidying up and filling the welds - which you will also have to do

 

Richard

[bottle]

 

Applicability – ventilators, doors, windows and hatches that can be closed without the use of tools must not be included in the calculations as these are not considered fixed ventilation

Applicability – permanent and measurable gaps around doors and windows when the windows or doors are fully closed can be taken into account as part of the fixed ventilation provision.

Applicability – in the event significant shortfalls in fixed ventilation are determined take the actions described in Appendix A. A significant shortfall is:

· where the total effective area of fixed ventilation is 50%, or less, of the calculated fixed ventilation requirement; or,

· where the total effective area of fixed ventilation is less than the calculated fixed ventilation requirement for appliances with continuous-burning flames; or,

· where there is no high or no low-level fixed ventilation.

 

FIXED VENTILATION

Fixed ventilation is ventilation that cannot be closed without the use of tools.

Note 1 – Ventilators, doors, windows, hatches and any other openings, which can be fully closed, must not be included in the ventilation calculation.

Note 2 – Ventilators, doors, windows, hatches and any other openings, modified so they cannot be fully closed without the use of tools should only have their minimum fixed ventilation area included in the calculation.

FACTORS AFFECTING TOTAL EFFECTIVE AREA OF FIXED VENTILATION

The total effective area of fixed ventilation’ is: the total area of fixed ventilation provision, as measured.

Each ventilator, door, window, hatch and any other openings should be measured carefully to determine their individual effective area of fixed ventilation.

Careful examination must be made of each ventilator to determine the presence of any device which would reduce the clear air opening e.g. filter, insect screen, fan blades.

Where filters or screens are fitted, they must also be in a clean and serviceable condition as partial or complete blockage of the clear air openings could make the ventilator totally ineffective.

Louvered doors are a common form of providing fixed ventilation and the effective area needs to be carefully measured.

The total effective area of fixed ventilation is designed to provide:

· combustion air for appliances that are not room-sealed;

· for the evacuation of combustion products from appliances that are not room sealed;

· renewal of fresh air for habitation and comfort.

CALCULATION OF FIXED VENTILATION REQUIREMENTS

The formula used to calculate the fixed ventilation requirement is derived from BS 5482-3 Annex B (Code of practice for domestic butane and propane gas-burning installations —Part 3: Installations in boats, yachts and other vessels), but as extended by BS8511 Annex A (Code of practice for the installation of solid fuel heating and cooking appliances in small craft) to address solid fuel stoves and other appliances.

The formula for calculating the fixed ventilation requirement ( in mm2 )is as follows:

= [2200 x U] + [650 x P] + [550 x H] + [440 x F], where:

U = input rating for all unflued appliances (inc. cookers) (in kW)

P = number of persons for which the accommodation space is designed

H = nominal output rating of all open-flued solid fuel appliances (in kW)

F = input rating for all open-flued appliances (in kW)

K

BSS ECPs Privately Owned & Managed boats Page 78 [Public Edition 3, Rev. 0 – January 2013]

The calculation is to be specifically made for each installation with reference to appliance input ratings (output ratings for solid fuel appliances) taken from manufacturer’s plates, manuals or accumulated reference lists. It is not acceptable or appropriate to estimate or guess fixed ventilation requirements.

Examiners will retain a written record of the ventilation calculation for each examination made. The record will detail all appliances and ratings and whether it is flued or not.

CLOSED-FLUE APPLIANCES

From the Glossary definition, ‘open-flue’ appliances take their air for combustion from the space in which they are installed. Open-flue appliances can be identified by the presence of a draught diverter which provides a draught break between the primary flue on the appliance and the secondary flue connecting the draught diverter and the flue terminal.

Closed-flue appliances also take their air for combustion from the space in which they are installed, but the flue is closed from the space due to the absence of a draught diverter. Solid fuel appliances usually have closed-flues, as do many central heating boilers.

In regard to factors ‘H’ and ‘F’ the formula for calculating the fixed ventilation requirement refers to ‘open-flued’ appliances. However, the output ratings of all closed-flue solid fuel appliances must also be included within ‘H’, and the input ratings of all other closed-flue appliances must be included within ‘F’, when making the calculation.

Closed-flue appliances must not be confused with balanced (or room-sealed) appliances which are not included in the calculation.

SOLID FUEL APPLIANCES

In the absence of manufacturer’s details, an output rating of 5kW may be assumed as forming a reasonable basis for the fixed ventilation requirement for solid-fuel appliances.

APPLICATION

The calculation should be applied to any part of the vessel containing a fuel burning appliance that:

· is normally divided as a separate compartment;

· can be temporarily divided except by curtaining.

HIGH AND LOW LEVEL VENTILATION

The total effective area of fixed ventilation (at least up to the calculated fixed ventilation requirement) should be divided as equally as practicable between high - and low-level.

Where the total effective area of fixed ventilation exceeds the calculated fixed ventilation requirement there is no requirement for the excess fixed ventilation provision to be divided as equally as practicable between high - and low-level.

Low-level ventilation can be achieved by spillage of cold air from vents in doors and/or bulkheads or by means of ducting from a higher level.

[Naughty Cal]

Make your boat seagoing then you don't need to bother with fixed ventilation!

[Polishicebreaker]

OK, another aspect. Should you choose to have the holes welded up, you'll probably distort the roof. Making that look good is a nightmare, far worse than tidying up and filling the welds - which you will also have to do

 

Richard

yes thats a good point, I already did this when plating where the flue pipe was before. My consolation is that the roof isn't a very good shape anyway so not too bothered but I'd rather not do it again. Are there any welding techniques to minimise this?

 

cheers Ed

[Polishicebreaker]

 

 

Applicability – ventilators, doors, windows and hatches that can be closed without the use of tools must not be included in the calculations as these are not considered fixed ventilation

Applicability – permanent and measurable gaps around doors and windows when the windows or doors are fully closed can be taken into account as part of the fixed ventilation provision.

Applicability – in the event significant shortfalls in fixed ventilation are determined take the actions described in Appendix A. A significant shortfall is:

· where the total effective area of fixed ventilation is 50%, or less, of the calculated fixed ventilation requirement; or,

· where the total effective area of fixed ventilation is less than the calculated fixed ventilation requirement for appliances with continuous-burning flames; or,

· where there is no high or no low-level fixed ventilation.

 

FIXED VENTILATION

Fixed ventilation is ventilation that cannot be closed without the use of tools.

Note 1 – Ventilators, doors, windows, hatches and any other openings, which can be fully closed, must not be included in the ventilation calculation.

Note 2 – Ventilators, doors, windows, hatches and any other openings, modified so they cannot be fully closed without the use of tools should only have their minimum fixed ventilation area included in the calculation.

FACTORS AFFECTING TOTAL EFFECTIVE AREA OF FIXED VENTILATION

The total effective area of fixed ventilation’ is: the total area of fixed ventilation provision, as measured.

Each ventilator, door, window, hatch and any other openings should be measured carefully to determine their individual effective area of fixed ventilation.

Careful examination must be made of each ventilator to determine the presence of any device which would reduce the clear air opening e.g. filter, insect screen, fan blades.

Where filters or screens are fitted, they must also be in a clean and serviceable condition as partial or complete blockage of the clear air openings could make the ventilator totally ineffective.

Louvered doors are a common form of providing fixed ventilation and the effective area needs to be carefully measured.

The total effective area of fixed ventilation is designed to provide:

· combustion air for appliances that are not room-sealed;

· for the evacuation of combustion products from appliances that are not room sealed;

· renewal of fresh air for habitation and comfort.

CALCULATION OF FIXED VENTILATION REQUIREMENTS

The formula used to calculate the fixed ventilation requirement is derived from BS 5482-3 Annex B (Code of practice for domestic butane and propane gas-burning installations —Part 3: Installations in boats, yachts and other vessels), but as extended by BS8511 Annex A (Code of practice for the installation of solid fuel heating and cooking appliances in small craft) to address solid fuel stoves and other appliances.

The formula for calculating the fixed ventilation requirement ( in mm2 )is as follows:

= [2200 x U] + [650 x P] + [550 x H] + [440 x F], where:

U = input rating for all unflued appliances (inc. cookers) (in kW)

P = number of persons for which the accommodation space is designed

H = nominal output rating of all open-flued solid fuel appliances (in kW)

F = input rating for all open-flued appliances (in kW)

K

BSS ECPs Privately Owned & Managed boats Page 78 [Public Edition 3, Rev. 0 – January 2013]

The calculation is to be specifically made for each installation with reference to appliance input ratings (output ratings for solid fuel appliances) taken from manufacturer’s plates, manuals or accumulated reference lists. It is not acceptable or appropriate to estimate or guess fixed ventilation requirements.

Examiners will retain a written record of the ventilation calculation for each examination made. The record will detail all appliances and ratings and whether it is flued or not.

CLOSED-FLUE APPLIANCES

From the Glossary definition, ‘open-flue’ appliances take their air for combustion from the space in which they are installed. Open-flue appliances can be identified by the presence of a draught diverter which provides a draught break between the primary flue on the appliance and the secondary flue connecting the draught diverter and the flue terminal.

Closed-flue appliances also take their air for combustion from the space in which they are installed, but the flue is closed from the space due to the absence of a draught diverter. Solid fuel appliances usually have closed-flues, as do many central heating boilers.

In regard to factors ‘H’ and ‘F’ the formula for calculating the fixed ventilation requirement refers to ‘open-flued’ appliances. However, the output ratings of all closed-flue solid fuel appliances must also be included within ‘H’, and the input ratings of all other closed-flue appliances must be included within ‘F’, when making the calculation.

Closed-flue appliances must not be confused with balanced (or room-sealed) appliances which are not included in the calculation.

SOLID FUEL APPLIANCES

In the absence of manufacturer’s details, an output rating of 5kW may be assumed as forming a reasonable basis for the fixed ventilation requirement for solid-fuel appliances.

APPLICATION

The calculation should be applied to any part of the vessel containing a fuel burning appliance that:

· is normally divided as a separate compartment;

· can be temporarily divided except by curtaining.

HIGH AND LOW LEVEL VENTILATION

The total effective area of fixed ventilation (at least up to the calculated fixed ventilation requirement) should be divided as equally as practicable between high - and low-level.

Where the total effective area of fixed ventilation exceeds the calculated fixed ventilation requirement there is no requirement for the excess fixed ventilation provision to be divided as equally as practicable between high - and low-level.

Low-level ventilation can be achieved by spillage of cold air from vents in doors and/or bulkheads or by means of ducting from a higher level.

 

excellent, thanks.

[Steve 210859]

Hi

 

My Name is Steve Williams, I am a Boat Safety Scheme examiner, currently registered and authorised to undertake BSS Certification on Private vessels on the inland waterways.

 

I would like to point that that where you have Gas, Diesel or Solid Fuel appliances on your vessel it is always a mandatory requirement that a BSS examiner calculate the minimum level of fixed ventilation available in the upper and lower segments of your vessel (i.e. above and below Gunwales).

 

This calculation is then compared to the total ventilation requirements of your on board appliances. Naturally as BSS examiners and for your own safety you should have more fixed ventilation available in the vessel than is required for your appliances. However, not having sufficient fixed ventilation available will not affect the status of your vessel in regards to meeting, or not meeting the requirements of the BSS examination. This is because calculations of fixed ventilation are 'Advisory' and do not affect whether the examiner will pass or fail your vessel.

 

In the case of insufficient fixed ventilation in your vessel then the examiner will issue you a warning notice stating such, but your vessel will pass the Examination.

 

I WOULD STRONGLY RECOMMEND THATA VENTILATION CALCULATION FOR YOUR VESSEL BE UNDERTAKEN BEFORE YOU MAKE ANY ALTERATIONS TO THE VESSEL.

 

Also, ANY Alterations to your vessel MAY HAVE the ability to INVALIDATE your BSS Certificate and thereby could affect your insurance.

 

Please be careful.

 

Regards

 

Steve Williams

BSS Examiner PIN614

iwabss-limited.co.uk

[ditchcrawler]

 

 

Applicability – ventilators, doors, windows and hatches that can be closed without the use of tools must not be included in the calculations as these are not considered fixed ventilation

Applicability – permanent and measurable gaps around doors and windows when the windows or doors are fully closed can be taken into account as part of the fixed ventilation provision.

Applicability – in the event significant shortfalls in fixed ventilation are determined take the actions described in Appendix A. A significant shortfall is:

· where the total effective area of fixed ventilation is 50%, or less, of the calculated fixed ventilation requirement; or,

· where the total effective area of fixed ventilation is less than the calculated fixed ventilation requirement for appliances with continuous-burning flames; or,

· where there is no high or no low-level fixed ventilation.

 

FIXED VENTILATION

Fixed ventilation is ventilation that cannot be closed without the use of tools.

Note 1 – Ventilators, doors, windows, hatches and any other openings, which can be fully closed, must not be included in the ventilation calculation.

Note 2 – Ventilators, doors, windows, hatches and any other openings, modified so they cannot be fully closed without the use of tools should only have their minimum fixed ventilation area included in the calculation.

FACTORS AFFECTING TOTAL EFFECTIVE AREA OF FIXED VENTILATION

The total effective area of fixed ventilation’ is: the total area of fixed ventilation provision, as measured.

Each ventilator, door, window, hatch and any other openings should be measured carefully to determine their individual effective area of fixed ventilation.

Careful examination must be made of each ventilator to determine the presence of any device which would reduce the clear air opening e.g. filter, insect screen, fan blades.

Where filters or screens are fitted, they must also be in a clean and serviceable condition as partial or complete blockage of the clear air openings could make the ventilator totally ineffective.

Louvered doors are a common form of providing fixed ventilation and the effective area needs to be carefully measured.

The total effective area of fixed ventilation is designed to provide:

· combustion air for appliances that are not room-sealed;

· for the evacuation of combustion products from appliances that are not room sealed;

· renewal of fresh air for habitation and comfort.

CALCULATION OF FIXED VENTILATION REQUIREMENTS

The formula used to calculate the fixed ventilation requirement is derived from BS 5482-3 Annex B (Code of practice for domestic butane and propane gas-burning installations —Part 3: Installations in boats, yachts and other vessels), but as extended by BS8511 Annex A (Code of practice for the installation of solid fuel heating and cooking appliances in small craft) to address solid fuel stoves and other appliances.

The formula for calculating the fixed ventilation requirement ( in mm2 )is as follows:

= [2200 x U] + [650 x P] + [550 x H] + [440 x F], where:

U = input rating for all unflued appliances (inc. cookers) (in kW)

P = number of persons for which the accommodation space is designed

H = nominal output rating of all open-flued solid fuel appliances (in kW)

F = input rating for all open-flued appliances (in kW)

K

BSS ECPs Privately Owned & Managed boats Page 78 [Public Edition 3, Rev. 0 – January 2013]

The calculation is to be specifically made for each installation with reference to appliance input ratings (output ratings for solid fuel appliances) taken from manufacturer’s plates, manuals or accumulated reference lists. It is not acceptable or appropriate to estimate or guess fixed ventilation requirements.

Examiners will retain a written record of the ventilation calculation for each examination made. The record will detail all appliances and ratings and whether it is flued or not.

CLOSED-FLUE APPLIANCES

From the Glossary definition, ‘open-flue’ appliances take their air for combustion from the space in which they are installed. Open-flue appliances can be identified by the presence of a draught diverter which provides a draught break between the primary flue on the appliance and the secondary flue connecting the draught diverter and the flue terminal.

Closed-flue appliances also take their air for combustion from the space in which they are installed, but the flue is closed from the space due to the absence of a draught diverter. Solid fuel appliances usually have closed-flues, as do many central heating boilers.

In regard to factors ‘H’ and ‘F’ the formula for calculating the fixed ventilation requirement refers to ‘open-flued’ appliances. However, the output ratings of all closed-flue solid fuel appliances must also be included within ‘H’, and the input ratings of all other closed-flue appliances must be included within ‘F’, when making the calculation.

Closed-flue appliances must not be confused with balanced (or room-sealed) appliances which are not included in the calculation.

SOLID FUEL APPLIANCES

In the absence of manufacturer’s details, an output rating of 5kW may be assumed as forming a reasonable basis for the fixed ventilation requirement for solid-fuel appliances.

APPLICATION

The calculation should be applied to any part of the vessel containing a fuel burning appliance that:

· is normally divided as a separate compartment;

· can be temporarily divided except by curtaining.

HIGH AND LOW LEVEL VENTILATION

The total effective area of fixed ventilation (at least up to the calculated fixed ventilation requirement) should be divided as equally as practicable between high - and low-level.

Where the total effective area of fixed ventilation exceeds the calculated fixed ventilation requirement there is no requirement for the excess fixed ventilation provision to be divided as equally as practicable between high - and low-level.

Low-level ventilation can be achieved by spillage of cold air from vents in doors and/or bulkheads or by means of ducting from a higher level.

 

But he does NOT have to comply with it if he is not renting his boat out. its advisory

Edit

Steve got there first

Edited August 17, 2013 by ditchcrawler

[Polishicebreaker]

All very useful info, thanks!! I'll speak to my examiner as he's due a visit soon.

 

So is all the BSS just advisory?

[RLWP]

All very useful info, thanks!! I'll speak to my examiner as he's due a visit soon.

 

So is all the BSS just advisory?

 

NO!!

 

But the ventilation stuff is

 

Richard

[Peter Reed]

that sounds sensible thanks. I'll have a small gas boiler and a 5Kw stove in an open plan cabin thats around 30' x 10'. My friend suggested vents in the cabin sides rather than roof, also some in the doors. I also have wooden windows that are sealed but must provide some ventilation, hopefully not too much though if my Joinery is up to scratch!

Drill a dozen holes in each wooden window. Job's a goodun.

[Ex- Member]

Mushroom vent ventilation is not only way over the top it's placed in the highest part of the boat, so in winter all the hottest air you produce goes straight through the roof. We have 5 mushroom vents in total, that's equal to one big hole in the boats roof.

 

If you measured the gaps that currently exists in doors & hatches on your boat and don't apply any draft excluder to those gaps, it's likely you'll have ample ventilation available if mushroom vents not actually fitted at all.

 

All through the winter we put bungs in all the mushroom vents with just a 15mm hole through the bung, this meant we ran the heating on minimum setting for most of the winter period. It's completely ridiculous to operate vents in an area that most of the expensively produced heat will immediately escape through. Of course gaps in doors and hatches will lose some heat, but not the hottest heat and overall a fraction of the heat that's lost through a mushroom vent.

 

The gaps around the boats steel cratch doors alone when bolted shut I've calculated at 7100mm^2 that's averaging a conservative 1mm gap all around and centre join. Our side doors 3100mm^2

 

So over 10,000 Sqmm 4 times that of mushroom vents.

 

There's also the 1.6m pidgeon hatch where 2mm gap exists for the centre hinge so another 3200mm^2

 

The same applies to the side doors

 

I believe a 4 inch mushroom vent is around 2500mm^2

 

I think I'll completely block them this winter given these figures.

[Michael Wooding]

As the ventilation requirements are advisory only, how on earth could changing them invalidate an existing BSC? Stuff and nonsense!

 

Mike

[Steve 210859]

Hi,

 

Steve Williams here again. Sorry i thought i was clear in my reply earlier. What I said was:-

 

Also, ANY Alterations to your vessel MAY HAVE the ability to INVALIDATE your BSS Certificate and thereby could affect your insurance.

 

Emphasis on the ANY. Mike is correct, alterations to the ventilation will not invalidate the BSS Certificate for the vessel.

 

Unless of course you rent your vessel out, in which case Ventilation requirements are MANDATED in the 2002 ECPs for hire craft and minimum levels must be met.

 

Alterations to any or all of the vessel's other systems MAY HAVE the ability to INVALIDATE your BSS Certificate and thereby could affect your insurance.

 

Hope this clarifies my earlier post.

 

Regards

 

Steve Williams

BSS Examiner PIN614

Iwabss-limited.co.uk

[RLWP]

 

 

I think I'll completely block them this winter given these figures.

 

That's right. Screw them down until the dome touches the base for winter.

 

Properly designed ones used to have a wing-nut type thing on the end of the thread to do this from inside the cabin

 

Richard

[Ex- Member]

 

That's right. Screw them down until the dome touches the base for winter.

 

Properly designed ones used to have a wing-nut type thing on the end of the thread to do this from inside the cabin

 

Richard

 

Hi Richard

 

I didn't know that, clever idea.

 

The bungs we use are simply circles cut from Ethafoam with a hole drilled through the centre, the hole makes it easy to remove with your finger as well as retaining some ventilation. Etha foam is quite dense and has insulating properties.

 

The other point about doing this is as your boat will become much more heat efficient it will reduce condensation. There's an argument that good ventilation reduced condensation, but in reality sufficient heat combats it too, and if all that heat is going through the roof then it's not going to help with condensation problems.

[bottle]

I shall leave mine open, the boats to hot in the winter.