Floor-level draughts in an old cottage are sometimes excused as 'the house breathing'. Cold air blowing on people is not properly organised ventilation. A gap may supply too much in one place while barely helping a closed bedroom. Air through floor voids may not come directly from a clean outdoor location.
First ask: moving air or simply cold?
Cold floors and a draught can feel similar, but require different solutions. If the floor surface is cool because of insufficient insulation, filling the joints will not in itself provide the missing thermal resistance. If air clearly moves through a skirting-board joint, the leakage route matters. Sometimes both problems occur together, so it is useful to record them separately.
Note the precise location and conditions: one corner or the whole perimeter, only on windy days or constantly, the ground floor or a floor above a basement. Check whether the sensation changes when the cooker hood is switched on. This information can reveal a connection with pressure changes. It does not replace measurement, but helps the specialist avoid searching the whole home at once.
Where may the route begin?
A visible gap beside a skirting board is sometimes only the final point of a longer air route. Air can enter through the plinth, a floor junction, pipe penetrations or a leaky part of the basement. Sealing only the outlet into the room may leave another route and a hidden moisture problem. Inspection of the construction and airtightness layer is therefore important before final finishes.
The PNNL air-movement explanation distinguishes controlled from uncontrolled airflow. For a home, the practical distinction is very clear: a designed opening can be calculated, maintained and coordinated with extraction. The permeability of a random gap changes daily with wind and other pressure sources. Such an opening should not be retained as the only intended ventilation.
Why not spray-seal everything blindly?
Sealing is generally useful, but old timber structures require an understanding of moisture conditions. Room air leakage must be distinguished from a ventilated gap provided for the construction. For example, closing underfloor vents specified by the designer is not the same as putting the floor's airtightness layer right. One action may reduce draughts, while the other changes how timber dries.
Also first assess whether there is water ingress, mould or rot. The EPA moisture guide regards removal of the moisture source as a central part of mould prevention. A new skirting board or foam strip cannot replace repair of damaged construction. A damaged area that has been covered merely becomes harder to notice.
Illustrative example: cold only beside the external wall
Suppose the windows in a timber home have been replaced, but draughts remain along two external walls. The owner plans to install underfloor heating in the hope that it will remove the problem. Heating can change the surface temperature, but does not provide for sealing the airflow route. If the draught remains, some of the additional heat will be used to compensate for its effects.
The inspection first checks the floor-to-wall junction, underfloor condition and existing ventilation. A detail for repairing the appropriate layers is drawn up. Separately, the way rooms will receive outdoor air after sealing is specified. Comfort-related work is then not set in opposition: the construction is repaired while necessary ventilation is ensured, rather than leaving a random gap 'just in case'.
What to prepare for inspection
Photograph the locations before dismantling, include the room plan and describe the floor construction if it is known. Photographs of old renovation work are often more valuable than guesses about what is beneath the finish. State whether the home has a basement, stove, fireplace or a hood that discharges outdoors. These details can affect the sequence of inspection and sealing work.
Thermal imaging or an airtightness test may help, but the results must be interpreted by a specialist who knows the measurement conditions. A colder patch is not always an air gap. A thermal image alone, without temperatures, weather conditions and knowledge of the construction, cannot justify an entire reconstruction. Ask not only for a coloured picture, but also for a clear conclusion identifying which defect the particular sign confirms.
Room air and construction-void air differ
Air entering from a basement or underfloor void can carry odours and other unwanted substances. This is an important reason not to regard every movement of air as a fresh-air supply. The EPA indoor air-quality guide emphasises the importance of pollution sources and entry routes. A filter in the middle of the room does not replace putting an unknown air route right either.
If there is a persistent basement smell, inspect not only the floor but also pipe penetrations and unsealed service openings. Do not pour odour-masking products into the construction or use them as insulation. The origin must be understood, especially when moisture is also noticeable. Dismantling the construction must be safe; unknown old materials should not be sanded or broken before their composition has been assessed.
Agree exactly what the contractor repairs
It is worth listing the finishing of visible joints, restoration of the airtightness layer and possible structural repairs separately in the quotation. These tasks may look similar only in the final photograph. If the construction was not opened during the first inspection, the proposal must retain a clear boundary of uncertainty: what can be established now and what must be assessed after exposing the detail. This helps avoid unexpected changes in work scope and an unfounded promise that one material will resolve every sign of cold.
What is a reasonable outcome?
After the work, no unexplained air entry should remain at the floor edges. At the same time, a clear intended ventilation route for the rooms and suitable moisture conditions in the construction must be retained. These are three related but different objectives. It is worth separating them in the contractor's proposal so that 'we sealed it' is not presented as completion of every indoor-climate issue.
Keep photographs taken before and after the work, descriptions of the materials used and layouts of concealed details. If floors or pipework are changed later, this information will protect against new unplanned openings. Compare the sensation in similar weather conditions, rather than one calm day with an earlier storm. Ventilation principles can be reviewed in this explanation, and site photographs can be submitted in an enquiry.
Information sources
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