Environmental Control and the Pipe Organ
Conacher & CompanyEstablished 1854 Pipe Organ Builders |  |
The following advice on heating is based on a leaflet issued by The Federation of Master Organ Builders
Conacher & CompanyEstablished 1854 Pipe Organ Builders | |
The following advice on heating is based on a leaflet issued by The Federation of Master Organ Builders
Damage to Organs through abnormal heating and atmospheric conditions.
In recent times and all over the country, organs have been seriously deranged or damaged by over-heating with increasing frequency and are becoming more costly to repair.
It is not a new problem. Over some forty years it has become more widespread and increasingly severe.
The cause is most often an unaccustomed heating during periods of very cold or exceptionally dry weather. All too often it seems to occur soon after a tuner's visit yet it is generally due to causes outside the direct control of the organ builder.
History of the problem.
In past times churches were not heated to levels comparable to domestic standards and most often for week-ends only. Indeed it was customary to wear outdoor clothing at services and very modest winter heating temperatures sufficed.
Advances in the space heating of public buildings have brought a demand for comfortable temperatures in church. Automatic firing and self-regulation makes this practical for an increasing number of churches, both ancient and newly built. These new standards are welcome but it should be realised they bring new problems.
The basic causes.
Prolonged or extra heating in severe cold weather. A change to all-week background heating. A new standard of comfort made possible with a new or improved system. Any of these makes a significant change in the condition of the atmosphere in which the organ and other church furniture stands. The air becomes drier and the difference between summer and winter is in greater contrast.
The organ is a complex construction of fine timbers, well seasoned before being wrought to shape. Over the years it becomes naturally adjusted, in equilibrium with the established range of winter warming, spring or autumn moistness and summer heat. Any large change in the dryness or dampness of the air in church affects all woodwork, organ and furniture, which no matter how mature or seasoned, will shrink or expand with these changes in the atmospheric moisture content Equal variations in atmospheric humidity do not bring about equal movements in timbers, shrinkage being cumulative.
In older instruments especially, there is only a limited tolerance of this natural movement. Beyond this, destructive stresses arise that cause severe derangement of mechanism. This is especially so if the change in atmospheric condition is large and rapid.
When air is heated it expands and becomes drier. The greater the heating involved to reach the desired comfort level the greater the drying effect. This desiccated air thirstily draws moisture from furniture and fabric. In severe cases personal discomfort is experienced due to irritation of the respiratory passages.
For reasons of cost, it is rare for church heating systems to have full air conditioning or even means for re-humidifying the heated air. Indeed in many modern systems no built-in means is possible.
Measurement means and values.
This condition of the atmosphere can be expressed in terms of relative humidity (RH) as a percentage of saturation. Saturation is 100% RH at which fog or precipitation will occur.
An instrument called a Hygrometer is used for measurement. The simple hair type with convenient direct reading dial is not expensive and can be very informative.
In the United Kingdom the average outdoor humidity is about 80% RH. This reading is not unusual in midweek unheated churches, with temporarily lower values during old-style moderate week-end heating, of around 55% to 60% RH.
Heating to new levels around 60°F to 68°F produces conditions of much greater dryness. Air directly over or near hot radiators or pipes or at delivery grids of hot air systems, reaches very much higher temperatures, becoming parched and inevitably drawing moisture from and desiccating all woodwork it surrounds.
Although measurements differ in various parts of the country, where the organ was not built for modern heating or contains parts of old-style construction, the air moisture content (Relative Humidity) should broadly be about 65% and not fall for long to as low as 55% or rise much above 75%. Readings below 50% indicate danger and, if frequent, damaging stresses and trouble will certainly develop in complex wooden structures such as the organ windchests or pneumatic actions.
Remedial measures.
Entirely new organs and major parts can and should be so made to withstand the wide ranging atmospheric conditions that well regulated modern heating imposes. Even so, care is necessary at times when heating is boosted during cold snaps.
Gradual change is less damaging than rapid heating.
Unfortunately no amount of skill and manipulation can condition organ parts of older construction to withstand these drier atmospheres with certainty. After a number of years equilibrium will be reached, but too often only after costly repair or reconstruction. Some care and deliberate tempering of the dry conditions around and an the organ is still advisable. There are means available.
Moderating the heating.
The demand for more comfortable levels of heating in church is likely to extend and to be met in one way or another. A counsel of low level heating around the organ, while sound and useful is not likely to be generally accepted. Where a valuable old instrument is concerned and where no other remedial measures can be afforded it is the only way to preserve it against costly damage.
In these circumstances the heat around the organ should be no more than a week-day background of say 50°F, boosted at week-ends to say 58°F or at most 60°F.
During very cold weather, below freezing point outdoors, even this level may cause air drying to exceed safe limits. Heating should then be for as short a spell as possible if desiccation damage is to be avoided.
Ventilation.
Where the instrument stands in a chamber, local ventilation may be beneficial. The provision of an opening to outside air high up in an elevated organ chamber is a practical way of reducing the unwanted heat from risen hot air trapped therein, but the air replacing it may bring new problems. Ventilation in the church itself may be preferable. Opening windows is not a substitute for moderating local heating by proper means as it only wastes fuel. However, some ventilation is desirable.
Rehumidisation.
The practice of providing a few small water containers inside an or gan is usually misconceived and rarely of any corrective value. The water area is small and, especially when the surface becomes dusty, the amount of water evaporated trifling, as can be deduced from the infrequent refilling required.
Water evaporation pans of effective area require much space and constant attention if they are to remain serviceable and inoffensive. With expert planning, given space and assured air circulation, they can be effective in a general way only, lacking self regulation as they do.
Industrial type humidifying devices are available. Some are unsuitable, lacking simple regulation and needing technical servicing. In general there are two types of humidifiers available for organ use.
Those mechanically atomising water into a fine mist, or aerosols, and those delivering moistened air under slight pressure within or outside the organ parts. The aerosol type could be of use in a confined but uncrowded organ chamber for instance, but never as a source of moist air delivered to the blower. These small units cannot condition the air around an instrument in an open position to any useful effect. They are more suited to domestic and office use where lack of self regulation is of little consequence and should only be used relative to organs under experienced guidance to avoid risk of damage by excess.
The pressurised moist air system has been developed for organ use. It is the most generally applicable method. Its automatic regulation is good, an important factor in apparatus infrequently serviced. A humidifier correctly applied can save its cost in avoiding greater expense in organ repairs made necessary by overheating desiccation.
Heating Systems and the organ.
Hot water heating pipes should not pass through an organ.
Radiators and hot pipes in or near to an organ chamber must be avoided unless there are operative re-humidising means available and then only on the specific advice of a responsible organ builder.
Where there is a hot air system, delivery grilles or grids should be well away from the organ. Those unavoidably close by should be carefully regulated to give minimum requirements.
This is especially so where the instrument is in an elevated organ chamber into which the rising hot air will be trapped.
Some modern examples of this system deliver super-heated air which rises rapidly to form an overhead blanket of hot dry air particularly destructive to an organ in a lofty position.
Treatment of these cases is difficult and they require individual study. Hot water under-floor heating, because the source temperatures are low and rapid boosting is not possible, rarely causes desiccation provided the heated surfaces are not beneath any part of the organ.
Where there is an old instrument, air temperatures should be kept as moderate as possible.
The same observations apply to electric night-store heating. Any system of rapid church heating relying solely on warm air convection from say, electric or fan assisted radiators switched on only when required and not having time to warm the fabric of the building, has to raise the air temperature much above normal.
This produces excessive dryness relative to the comfortable conditions achieved. The ill effects are felt by the congregation as well as the organ woodwork and tuning and can be moderated by restraining the heating time to as short a period as possible, although subsequent damaging condensation may not be avoided.
Rapid heating systems make good organ tune almost impossible unless there is some independent background heating, especially around the instrument. The location of the organ electric blower in relation to the heating furnace can be critical where modern firing systems are installed.
It is important to avoid drawing in heated air from this source. In these circumstances every endeavour should be made to arrange another air intake to the fan. It must be pointed out that not only the organ woodwork suffers, all the woodwork, fabric, furniture and fittings suffer to the same degree and may continue in their functions whereas the organ may not.
Therefore the attention of church authorities is drawn most seriously to this matter, for an organ is a valuable instrument, costly to repair once damaged.
It is uneconomic and usually impracticable, to attempt to adjust organs suffering from severe shrinkage to meet these temporary emergency conditions.
When normal atmospheric moisture returns much of the adjustment made will prove unnecessary and costly re-adjustment becomes unavoidable.
In the majority of cases there is no first aid action possible beyond amelioration by some simple rehumidisation programme, such as water sprinkling around the organ and on the church floor carried out under the organ builder's direction and supervision.
Before remodelling or installing a new heating system church authorities are strongly advised to consult their organ builder.