Can my British husband be exempt from the 90/180 rule when travelling with me, an Irish citizen?

Because you are an Irish citizen, you are an EU citizen. Your husband, as your UK-national spouse, can benefit from EU free-movement rules when he accompanies or joins you in another EU country such as Spain.

This means that periods when he is genuinely travelling with you as the family member of an EU citizen can be treated differently from an ordinary British tourist relying only on the standard 90-days-in-180 Schengen rule. For short visits, he should travel with evidence of the family relationship and of travelling together with you.

In practice, I would recommend carrying:

Your Irish passport. His UK passport. Your marriage certificate (ideally the original or a clear official copy). Evidence that you are travelling together, if it is not obvious from the booking.

For the pattern you describe — approximately 7 to 10 days per month — he would normally remain well within 90/180 anyway, so in most cases you would not need to rely on the EU-family-member exception. If you begin spending much longer periods in Spain, then it becomes more important to distinguish short visits from residence and to consider whether registration/residence formalities apply.

Owning a property in Estepona does not itself create residence rights or change the immigration rules.

Note: This is general information and not legal or tax advice. EU free-movement rights depend on the exact circumstances, including whether the non-EU spouse is accompanying or joining the EU citizen and the length/purpose of the stay. We recommend carrying proof of the family relationship and confirming any longer-stay plans with the Spanish authorities or a qualified immigration professional.

Official source: Your Europe (EU): travel documents for non-EU family members