From my observation thru the years

1. For urban BHs, there shall not be a problem of temperature @ night as the walls will slowly release the heat accumulated during the day. The problem of too cold may only apply to BHs @ Agriland.
2. I only find too hot esp. on ceiling and wall @ BHs that seem to be of a problem and by raising the humidity do solve the problem most of the time but as for the ceiling being too hot, no bird will build nest there so you need to find way to prevent the heating up of the ceiling by many methods like using Styrofoam over the ceiling or adding extra layer of asbestos or some using water or even to the extend of adding another roofing over the roof.
3. Light is definitely a problem so refrain from using light in the nesting area unless necessary as in darkness, you will be just a pillar to the birds to avoid but with lighting, you are another predator.
4. Less disturbance to the BH will ensure better increment to your BHs.
5. Some people try not using humidifiers in their BHs or possible because there isn't water supply to the bhs and there are some reported of success but from my point of view, these are due to the facts that their area maybe normally at agriland where cold and dampness arise without the usage of any help.

Just my points of views to share if you agree but if you don't, please enlighten me.

To me, the air circulation are mainly for us and lesser for the birds so that we don't suffocate inside the BH during our maintenance or harvesting. BIrds really can stand the Ammonia as any visit to successful Bhs will tell. If you can't, a visit to swiftlets cave would. So, no exhaust fan necessary at all for new BHs if your BH isn't hot and even V holes need to be reduced. Air circulation is for fresh air for the health of animal mostly of human origin which is very weak compare to other wild animals

My suggestion is to save your electricity on your exhaust fan and better spend it on me over a coffee and you learn more. ...just kidding hahaha.

Best of Luck to you.

By the way, a friend asked me on which is the best type of insects eggs powder and those using maybe able to help this friend although I never encourage people using such products.

ps. I really need your Exhaust fans as the ammonia really blind me at time but the birds seem to like it..........I may go and buy the WW 2 gas mask at secondhand/reject shop for my health.

Thanks Bros,

So no need to change nesting planks. That is good news to me.

I am hoping for the best after changing tweeters and speaker cables.

What more shall I do to hansten the increase in nests?

Hai, all sifu ...another question. I have a new bird house just open sound for 9 days. Have about 30++ bird staying. Problems is those bird only stay but never play at day time. They only play for first few days when the birdhouse start. Now hardly see any bird come to play at noon time, only come back at night. have change few pooling sound at UFO speaker but seem like not working. What should I do....

Yes,  external sound will only pull the swiftlet to your entrance hole and you need to make sure that the birds fly right into your BH by extending the sound to the interior of the BH by adding tweeters (exernal sound) into the nesting area and stop there; then the internal sound shall ake over from there.

Olden time, we use the cheapest wire and that cause the melting of wire but then we didn't use so many tweeters. The cheap wire maybe inferior and therefore easily to burn if too much current pass thru and it advantages was that it save your amplifier incase of short circuit in the system by melting away where else, nowaday with good quality wire, the amp. burn out if there is any short circuit in the system......many fellow owners asked about their constant burning of amps and I told them to check for any short circuit of tweeters in their system as most of these are cause by the accidentally shorting cause by birds.

So, if you are changing tweeters, make sure that the connection is secured and strong, otherwise, your next problem shall be a burned out amp.