yep mine are the same at the mo - it's just cold. if droppings are ok then they'll be fine.
if you want to know about drafts read this - it's a bit teckie tho!!
Purpose of Ventilation
The purpose of ventilation is to: Make fresh oxygen available to the respiratory system. Remove the exhaled gases and the gases produced by the droppings. Rid the loft of excess moisture so the RH will stay within the permissible levels. Help maintain the temperature at the proper level.
You may have to ventilate year round when you want to provide the loft with new oxygen and at the same time remove the accumulated harmful gases. Especially in the summer, when the temperature outside is high, ventilation is essential to remove the heat the pigeons produce. As the temperature rises the level of oxygen in the air goes down. For this reason we must ventilate more. During the winter, though we ventilate as little as possible by reason of the fact that we want to keep the loss of heat to a minimum. This minimum amount depends on the number of pigeons in the loft and the odor they produce.
Mechanics of Ventilation
A body of air which is trapped inside a closed area will put pressure on all sides whenever the temperature in that area is higher than the outside temperature. Heat is produced by the pigeons, the sun’s rays that penetrate the loft, and when available, other sources of heat. Within the loft the air will layer itself and the warmest layer will rise to the ceiling, while the coolest air is found near the floor. Whenever warm air meets the outside air and exchange will take place. Because of the built up pressure the warmer air will move out from the top of the loft while the colder air comes back in at the bottom, thus replacing the warmer and lighter air inside the loft. This, in brief, is the is the principle of natural ventilation.
Natural ventilation is the result of the temperature differences or a difference in weight between the air inside the loft and the outside air. If the difference is extensive the exchange happens quicker and as a result you have more natural ventilation.
The amount of natural ventilation can also be increased by the so called “chimney effectâ€. This effect is based on the idea that air pressure differences also depend on the difference in height between the air outlet and air intake. This difference can be increase by way of ducts.
Pressure Caused by Wind
There is more pressure placed on the side of the loft on which the wind is blowing and less pressure on the opposite side. When the ventilation openings are not properly covered, or in some way protected, they will help bring about unwanted side ventilation, because of the wind pressure. Another word for this type of ventilation is drafts. Nobody needs this! The best thing to do is locate the loft in relation to the prevailing winds so that this problem is kept to a minimum.
Ventilation System Requirements
Proper ventilation should: Be able to maintain the correct quality of air. Provide good quality air to all corners of the loft. Never cause drafts. Be both efficient and easy to regulate.